Showing posts with label raid. Show all posts
Showing posts with label raid. Show all posts
Wednesday, December 14, 2016
RAID 0 Recovery
RAID 0 Recovery
RAID 0 Recovery
Before you rush to recover RAID 0, you need to understand the causes of RAID 0 failure. There are two different types of RAID 0 failure:
- failure of one or several RAID 0 member disks;
- failure not associated with the member disks.
RAID 0 member disk failure
Since RAID 0 arrays are non-redundant, then if one of the member disks fails, then data that was on the failed disk is lost forever. Having data from the rest of the member disks you can try to recover files. However, only the files which are smaller than (N-1)*(block size) can be recovered. Even files smaller than that limit can be unrecoverable if the part of the file happens to be on a failed disk.
So in general, if one of the member disks fails beyond repair, it is impossible to recover data from RAID 0.
RAID 0 failures not associated with the loss of the member disks
Such RAID 0 failures include operator errors, controller failures, or RAID 0 controlling software failures. In this case RAID 0 configuration metadata is lost, but the member disks are working properly.
With these failures, it is possible to recover data from RAID 0. First, you should determine the array configuration. RAID 0 configuration includes:
- number of member disks,
- disk order, along with what disk was the first in the array,
- block size,
- start offset on the disks.
Manual RAID 0 recovery
How to determine the disk order
You can determine the disk order manually relying on the long text files, preferably log-files with timestamps. For searching the disk members for such files use any disk viewer tool, like WinHex. When a fragment of a suitable file would be found on one of the member disks it is needed to track what disk contains the next fragment and etc. This way, you can determine the disk order although it is impossible to find out what disk was the first.
How to determine the first disk
It is not difficult to determine what disk was the first in RAID 0. Once again, you need to use a disk viewer tool and search the member disks for:
- MBR in case of a hardware RAID - the disk that contains the MBR is the first RAID 0 disk.
- boot sector for a software RAID 0 - the disk that contains the boot sector at the beginning is the first disk.
How to determine block size (stripe size)
For a hardware RAID 0, you can determine block size by going over the possible values or look up what block size can be used in your RAID 0 implementation in the appropriate manual.
For a software RAID 0, use the standard value. For example, Windows uses a 128 sectors block for RAID 0.
How to determine start offset on the member disks
On a hardware RAID, data most likely starts at the start of the hard drive. This is equivalent to the offset of 0 (zero).
If a software RAID is used, the offsets are in most cases identical for all member disks. The offset to the start of the volume can be identified by locating the volume boot sector.
RAID 0 recovery with software
If the manual option seems too complex and time-consuming, try the automated RAID recovery software.
There are many tools capable of automatically recovering RAID 0 on the market (check the RAID recovery software comparison). These software utilize different algorithms (not necessary such as described above) and usually such tools are relatively expensive.
We offer a fully automated and free solution for the RAID 0 recovery situations. Our software ReclaiMe Free RAID Recovery determines the array configuration parameters for RAID 0, RAID 01/10, and RAID 5 using only the data contained on the member disks. Just download ReclaiMe Free RAID Recovery then select all the available member disks (dont forget to connect them to the PC separately), start RAID 0 recovery and get the recovered RAID 0 configuration. More instructions on how to recover RAID tutorial page.
Go to link download
Tuesday, December 13, 2016
RAID 5 RAID 6 Or other altErnativE
RAID 5 RAID 6 Or other altErnativE
RAID 5 RAID 6 Or other altErnativE?
Here we are with the next part of our RAID series. This time the article will concern RAID 5, RAID 6 and two alternatives – RAID 5E and 5EE. Take a look…
RAID 5
RAID 5 is one of the most popular implementations. It works almost the same as RAID 4 but with one difference. The parity bits are not recorded on a specifically prepared disk – they are dispersed throughout the matrix structure. What does this mean in the case of failure? Well, it is much easier to recover data (in case of failure of one disk). Also, the read speed is much higher (in comparison to RAID 0).
However, as usually happens, there are also some drawbacks. The necessity of calculating checksums causes a lower write speed. RAID 5 is also expensive in the case of the array reconstruction – if one of the disks have to be replaced after failure. Also read and write operations will slowdown in such case due to the need of calculating checksums.
RAID 5 is the best solution when we talk about data safety. In the case of failure the system will automatically rebuild the lost data so that they can be read (however, the current performance of the matrix will be reduced).
RAID 5
For more information about RAID 5 mode of action take a look here: “How does RAID 5 work? The Shortest and Easiest explanation ever!” by Janusz B?k.
RAID 6. The next level of excellence and complexity
RAID 6 is sometimes called RAID 5+1. It is because its mechanism is based on RAID 5. Generally it is RAID 5 but array enriched with one additional disk. Thus it contains two independent checksums. It is more reliable, but its implementation is more expensive.
RAID 6
RAID 6 is resistant so much so that its work will be impossible only after the failure of at least three disks. What does it mean? One important thing: It is two times more resistant than RAID 5. What is more, the speed of the whole system is higher than in the case of a single disk. It makes RAID 6 an almost ideal solution (if we do not take into account the costs of implementation).
Enhanced RAID
RAID 5E
RAID 5E (Enhanced) works similar to RAID 5. It stripes data and parity across all of the drives in array. The main reason is a built-in spare drive. Thanks to that, RAID 5E offers good data protection and better throughput. Also read and write operations are more efficient in the case of RAID 5E. It is because of this that such actions proceed faster in the case of four physical disks rather than three with an idle hot spare.
If we take into account the advantages of RAID 5E – good data protection, large storage capacity and high performance (higher than in the case of RAID 5) – we may ask: why it is less used in practice? The response should be sought in relation to its disadvantages.
The main drawback of such a solution is that the spare drive cannot be a part of any other array. So, if there is a need to implement its functionality to another array, preparing another spare drive is the only way. The second thing is RAID 5E supports only one logical drive in one array. And the most important – the thing which makes RAID 5E a useless solution in most cases – it is firmware-specific. Not every kind of controller can support this RAID level (in contrast to i.e. RAID 5).
RAID 5EE – Hot Space
RAID 5EE is an extended version of RAID 5E. It stripes data and parity across all of the drives in the array but it has a more efficient distributed spare. Its rebuild time is also faster.
RAID 5EE provides good data protection – like in the case of RAID 5. It also increases throughput – by using an additional hot spare disk in the array. Thanks to that, in the case of failure, when we have to replace the failed drive, the data from the “Hot Spare” emergency area are automatically transferred to it (to the new drive). The exempt space is than raised as an emergency space.
In this case, the difference between RAID 5E and 5EE is that the RAID 5EE spare is interleaved with the parity blocks (it does not use contiguous free space for the spare).
RAID 5EE requires a minimum of four drives. Just like RAID 5E it is also firmware-specific. It means we can expect problems with a controller. Also implementation costs, and any other – i.e. in case of failure, can be high. So we can say that this option is similar to RAID 5E.
Other possibilities
As it is easy to imagine, there are many solutions based on RAID. We have presented only the basic possible implementations. Although it does not mean the end. We can still point toward: RAID 1E, RAID x0, RAID 6E, 6EE and other. If you want to read about any of them, just let us know. We will do our best to give you the information you need.
Go to link download
Tuesday, December 6, 2016
RAID 5 and RAID 6
RAID 5 and RAID 6
RAIDs utilizing parity function(s)
RAID 5
RAID 5 utilizes the combination of striping and parity techniques. In case of RAID 5 the flow of data is split into the blocks of a certain size (block size) which are then written onto the member disks in turn. In each row one of the disks is assigned to store a certain checksum, so called parity function, which is calculated based on the data from other member disks in the row. In case of a single disk failure, the missing data can be calculated using the parity. In such a way fault tolerance is provided.
A minimum of three disks is required for RAID 5. Theoretically, the maximum number of the disks is not limited, but in practice, it is needed to take into account the controller capacity in case of a hardware RAID. The capacity of the array is (N-1) times the size of the smallest member disk for the array of N disks.
Thus, the capacity of one disk is used to store the parity function data to provide fault tolerance.
Reads in a RAID5 array
Read speed in RAID 5 is the similar to that of RAID 0 provided that the number of disks is the same. However, due to the fact that it is useless to read the parity data, the read speed is just (N-1) times faster but not N times as in RAID 0.
Writes in a RAID5 array
Writing data with the size less than the block size requires the following actions to be done:
- Read the old data block;
- Read the old parity block;
- Compare data in the old block with the newly arrived one. For every changed bit, change the corresponding bit in parity.
- Write the new data block;
- Write the new parity block.
As can be seen, the parity updates decrease the system write performance.
For writes which are equal to or bigger than the size of a row consisting of N data blocks, write speed is a bit faster because it is not required to read the old blocks and look for changes.
RAID 5 layouts
There are four different types of RAID 5 depending on where the parity blocks are located and in which order the data blocks are written (note that the first block in each row is colored red in the diagrams below):
Left and right arrays are determined by how the parity blocks are distributed onto the member disks. Synchronicity and asynchronicity define the order of the data blocks.
For RAID 5 recovery, all these parameters should be detected in addition to the block size, the start offset, and the order of the member disks.
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RAID 6
RAID 6 uses both striping and parity techniques but unlike RAID 5 utilizes two independent parity functionswhich are then written to two member disks. Typically, one of these parity functions is the same as in RAID 5(xor function), while the second is more complex. The parity data helps to recover data in case of simultaneous failure of two member disks.
A minimum of four disks is required to create RAID 6. The capacity of the array is (N-2) times the size of the smallest member disk for the array of N disks.
Read speed is (N-2) times faster than in case of a single disk - two disks in the row hold a parity which is useless to read. Such read speed values are roughly the same as in RAID 5.
There is no performance increase as to the write speed in RAID 6, because every new write requires a recalculation and update of two different parity blocks.
RAID 6 is rather expensive storage option. However, when it is needed a large and reliable storage, thenRAID 6 is one of the best choices, because it protects data if two disks failure happens. This can occur when:
- an array is rebuilding (so called rebuild time);
- a wrong disk is hot-swapped due to operator error.
Recovery considerations
When one disk is missing from a RAID 5 set, there is a certain speed penalty because the data stored on a missing disk must be recalculated. However, the recalculation is still significantly faster than having to try to read a physically damaged drive. Hence, you should avoid using drives that are known to be physically damaged (multiple bad sectors or similar issues) for recovery.
Although the RAID 6 can be rebuilt by the controller with N-2 disks available, ReclaiMe Free RAID Recovery requires N-1 disks to recover RAID6.
Go to link download
Monday, December 5, 2016
Data Recovery from RAID 5 to Computers failure
Data Recovery from RAID 5 to Computers failure
Introduction
So, youve ignored SAM and gone and run on a RAID 5. Then, through some elder gods handiwork, two of your disks drop off the RAID at the same time rendering your RAID 5 inaccessible. Your skin pales as you realise your last backup was *coughcough* months ago and close to useless. What to do? WHAT TO DO!?!
First things first - stop. Stop everything. Well, keep breathing, but stop everything else. Slow your mind and calm down.
Two disks dropping out of a RAID 5 simultaneously is odd. Its unlikely to be a hardware issue on both drives, so it could be a software issue.. possibly an incorrectly referenced or corrupt RAID config. If so, things may not be as bad as they seem and indeed, you may be able to recover everything.
This How-To addresses recovering data from failed RAID 5 arrays on Desktop PCs, a situation we all dread (and should avoid by running OBR 10). It is generic, and where assumptions are made they are stated.
Failing to have a recent backup is going to be expensive. Hopefully you already have the necessary hardware available to recover but if not, youll need to make a few purchases.
Depending on how the following steps pan out, you may not be successful in data recovery and you should accept that is a possibility. A lot of variables have to align to allow you to recover, but before admitting defeat stick your chin up, take a deep breath, and ... switch your PC off.
Steps (10 total)
First things first, shut your PC down.
Reason: your existing PC is a plague to your RAIDed disks at the moment, the controller can likely still access your disks and thinks its in its old raid config. While like this, there is the potential for extra writes to occur on those disks and this risk needs to be eliminated.
Keep it shut off. Dont switch it back on until you can pass the next step. Where possible, the entire RAID recovery needs to be performed in one long period without interruption.
Reason: your existing PC is a plague to your RAIDed disks at the moment, the controller can likely still access your disks and thinks its in its old raid config. While like this, there is the potential for extra writes to occur on those disks and this risk needs to be eliminated.
Keep it shut off. Dont switch it back on until you can pass the next step. Where possible, the entire RAID recovery needs to be performed in one long period without interruption.
To enable you to recover the data, youll need to have the necessary hardware.
1. A NAS or spare PC with significantly large network storage share.
Reason: an equal amount of space available somewhere else. If you had 3 x 1TB disks in RAID 5, you will need at least 3TB storage elsewhere. Likewise, if you had 5 x 3TB drives, youll need 15TB storage available on the network. This How To assumes you have a NAS with enough spare storage available, and is accessible on the network and ready for writing. Ka-ching!
Reason: an equal amount of space available somewhere else. If you had 3 x 1TB disks in RAID 5, you will need at least 3TB storage elsewhere. Likewise, if you had 5 x 3TB drives, youll need 15TB storage available on the network. This How To assumes you have a NAS with enough spare storage available, and is accessible on the network and ready for writing. Ka-ching!
2. An alternative disk connection. This can be a spare PC with spare disk ports, or an external HDD mount. This How To assumes you use a USB HDD dock
Reason: Since the RAID controller is the interface between your OS and the disks, your OS can only see the corrupted RAID, and may not even see the individual disks depending on the RAID corruption. Your disks will need to be removed from the existing controller and attached via an alternate means to a bootable Windows OS. If youre plugging them into a different PC, ensure the disk controller isnt the same model as the one controlling your failed RAID (which basically means ensure its a significantly different motherboard model). An external USB3 HDD dock is a safe bet, and not too expensive.
Reason: Since the RAID controller is the interface between your OS and the disks, your OS can only see the corrupted RAID, and may not even see the individual disks depending on the RAID corruption. Your disks will need to be removed from the existing controller and attached via an alternate means to a bootable Windows OS. If youre plugging them into a different PC, ensure the disk controller isnt the same model as the one controlling your failed RAID (which basically means ensure its a significantly different motherboard model). An external USB3 HDD dock is a safe bet, and not too expensive.
3. UPS me up, Scotty!
Reason: Youll need enough UPSs for all components during recovery. It/they need to be able to power a PC, a NAS, a switch/router and a USB HDD Dock in the event of a decent power failure. You know itll happen during this process (damn you elder gods!) so best protect against it.
Reason: Youll need enough UPSs for all components during recovery. It/they need to be able to power a PC, a NAS, a switch/router and a USB HDD Dock in the event of a decent power failure. You know itll happen during this process (damn you elder gods!) so best protect against it.
4. R-Studio Network Edition. Prepare to buy it, but not yet. Get the trial for now.
site: http://www.r-tt.com/
download: http://www.data-recovery-software.net/Data_Recovery_Download.shtml
store: https://secure.r-tt.com/cgi-bin/Store?id=1
Reason: Its the most stable, assured, and fastest RAID reconstruction/recovery tool Ive encountered (from recent experience, Jan 2013). There are other tools such as Zero Assumption Recovery that will probably suffice, but my personal recommendation is R-Studio. Since this How-To assumes youre recovering to and from a NAS or network share, the Network Edition is required. If you have uber space locally, the standard version is fine.
If you make it through to seeing your files later in this process, youll need to then purchase R-Studio, but in the meantime just download the trial. Install it.
site: http://www.r-tt.com/
download: http://www.data-recovery-software.net/Data_Recovery_Download.shtml
store: https://secure.r-tt.com/cgi-bin/Store?id=1
Reason: Its the most stable, assured, and fastest RAID reconstruction/recovery tool Ive encountered (from recent experience, Jan 2013). There are other tools such as Zero Assumption Recovery that will probably suffice, but my personal recommendation is R-Studio. Since this How-To assumes youre recovering to and from a NAS or network share, the Network Edition is required. If you have uber space locally, the standard version is fine.
If you make it through to seeing your files later in this process, youll need to then purchase R-Studio, but in the meantime just download the trial. Install it.
5. ReclaiMe Free RAID Recovery
site: http://www.freeraidrecovery.com/
download: http://www.freeraidrecovery.com/download.aspx
Reason: This automates finding the correct parameters for reconstructing a virtual RAID, and gives clear and concise R-studio instructions when finished. And its free! If youre handy with a hex editor, you can ignore this program and follow the R-Studio tutorials on finding RAID parameters (http://www.r-tt.com/Articles/Finding_RAID_parameters/). This How To assumes youre using this program, so install it.
site: http://www.freeraidrecovery.com/
download: http://www.freeraidrecovery.com/download.aspx
Reason: This automates finding the correct parameters for reconstructing a virtual RAID, and gives clear and concise R-studio instructions when finished. And its free! If youre handy with a hex editor, you can ignore this program and follow the R-Studio tutorials on finding RAID parameters (http://www.r-tt.com/Articles/Finding_RAID_parameters/). This How To assumes youre using this program, so install it.
Youre about to pull your PC apart and take those failed drives out. At this point, I recommend documenting everything and labeling cables and drive placements. Its not entirely necessary but its good to know what connected to what and where if you ever want to escalate this to a forensic Data Recovery Center. The more info the better.. and the cheaper.
Once documented, anti-static yourself and carefully remove your failed RAID drives.
Once documented, anti-static yourself and carefully remove your failed RAID drives.
One by one youll need to verify the physical integrity of your drives by running your vendors checking utilities.. e.g:
IBM/Hitachi -- Drive Fitness Test
SeaGate -- SeaTools
Western Digital -- WD Diagnostics/Lifeguard
So, plug in each drive to the dock and run the tests. DO NOT ATTEMPT ANY REPAIRS, run this in read-only mode ONLY. A random write to the could wipe out your chances of recovery. We just want to make sure your drives are physically OK.
If two disks fail because of a mechanical issue or your drives are dead, unfortunately youre hosed. Nothing to do except take it to a Data Recovery Centre. Youre probably looking at around $1,000 per recovered disk to get the experts to do it. Sorry, but this is by and large your only shot from here.
If one disk fails and the rest are fine you still have a shot. Continue.
If none fail and all your disks are fine, great! Continue!
IBM/Hitachi -- Drive Fitness Test
SeaGate -- SeaTools
Western Digital -- WD Diagnostics/Lifeguard
So, plug in each drive to the dock and run the tests. DO NOT ATTEMPT ANY REPAIRS, run this in read-only mode ONLY. A random write to the could wipe out your chances of recovery. We just want to make sure your drives are physically OK.
If two disks fail because of a mechanical issue or your drives are dead, unfortunately youre hosed. Nothing to do except take it to a Data Recovery Centre. Youre probably looking at around $1,000 per recovered disk to get the experts to do it. Sorry, but this is by and large your only shot from here.
If one disk fails and the rest are fine you still have a shot. Continue.
If none fail and all your disks are fine, great! Continue!
One by one, assuming your disks are physically fine, you need to use R-studio to take disk images of your failed RAID drives. If any disks failed the integrity check in Step 4, dont image those as it can corrupt the overall integrity of the virtual RAID later on - only image your physically OK disks.
To do this:
- ensure you have a Mapped Drive to your NAS or network storage share. This How To will assume you labeled it S: (R-Studio didnt like using UNC paths to take images)
- attach a HDD to the USB dock and ensure its powered up and visible in Windows (if not readable).
- open R-Studio
- in the drive list on the left, right-click your failed drive and select "Create Image"
- in the popup window, Main Tab, select Byte-to-Byte image, and for the Image Filename, rename it to be unique and on the mapped network share (e.g. "S:disk-01.dsk")
- click OK and wait until finished (could be hours to days)
- repeat for all disks, uniquely naming each image file on the file share.
To do this:
- ensure you have a Mapped Drive to your NAS or network storage share. This How To will assume you labeled it S: (R-Studio didnt like using UNC paths to take images)
- attach a HDD to the USB dock and ensure its powered up and visible in Windows (if not readable).
- open R-Studio
- in the drive list on the left, right-click your failed drive and select "Create Image"
- in the popup window, Main Tab, select Byte-to-Byte image, and for the Image Filename, rename it to be unique and on the mapped network share (e.g. "S:disk-01.dsk")
- click OK and wait until finished (could be hours to days)
- repeat for all disks, uniquely naming each image file on the file share.
So, youve physcially checked your disks and theyre OK. Youve successfully created images of those disks and theyre ready on the network. Now the clincher - you need to find if the RAID is able to be deciphered.
Close R-Studio
Open ReclaiMe Free RAID Recovery.
- Click on the drop-down arrow on the Disks icon up the top and select "Open disk image"
- Navigate to your NAS share and select all your uniquely named .dsk files you just made in R-Studio.
- back at the main screen, tick the checkboxes next to each of your disk images.
- click the big green Start RAID 5 icon up the top.
- let it do its thing. This step can take hours or days, or even weeks. For 4 x 2TB images it took 2 days on my system. Let it be and try to keep anything away from the PC and NAS and router/switch while it runs.
Close R-Studio
Open ReclaiMe Free RAID Recovery.
- Click on the drop-down arrow on the Disks icon up the top and select "Open disk image"
- Navigate to your NAS share and select all your uniquely named .dsk files you just made in R-Studio.
- back at the main screen, tick the checkboxes next to each of your disk images.
- click the big green Start RAID 5 icon up the top.
- let it do its thing. This step can take hours or days, or even weeks. For 4 x 2TB images it took 2 days on my system. Let it be and try to keep anything away from the PC and NAS and router/switch while it runs.
There is a "Confidence" meter shown during analysis. If this gets to 100% before the "Progress" meter then things are looking good. If the Progress meter gets to 100% while Confidence is low, the amount of data you can recover is diminished, if any. For RAID data recovery, as in life, high Confidence is what youre after.
When finished, ReclaiMe will give you instructions for R-studio. Copy it into a document and save/print it for reference later.
When finished, ReclaiMe will give you instructions for R-studio. Copy it into a document and save/print it for reference later.
Using the instructions given to you by ReclaiMe, follow them exactly. And by exactly, I mean exactly.
Heres an example what youre likely to have:
-------------------------------------------------------
These instructions are provided for R-Studio version 5.1
1. Launch R-Studio
2. On the toolbar, click "Open image". Enter "S:ST2000DM001-9YN164CC4C-Disk3.dsk" as the file name, click "Open"
3. On the toolbar, click "Open image". Enter "S:ST2000DM001-9YN164CC4C-Disk1.dsk" as the file name, click "Open"
4. On the toolbar, click "Open image". Enter "S:ST2000DM001-9YN164CC4C-Disk2.dsk" as the file name, click "Open"
5. On the toolbar, click "Create Virtual RAID". Then, select "Create Virtual Block RAID" from the dropdown menu.
6. Right click the disk list on the right, select "Add S:ST2000DM001-9YN164CC4C-Disk3.dsk" from the pop-up menu.
7. Right click the disk list on the right, select "Add S:ST2000DM001-9YN164CC4C-Disk1.dsk" from the pop-up menu.
8. Right click the disk list on the right, select "Add S:ST2000DM001-9YN164CC4C-Disk2.dsk" from the pop-up menu.
9. On the right side of the R-Studio window, set "RAID type" to "RAID5".
10. Below that, set "Block size" to "64 KB".
11. Below that, set "Block order" to "Left Asynchronous".
12. In the "Parents" table, enter "0 Sectors" as "Offset" in all rows.
13. Below the RAID diagram, click "Apply".
14. On the left panel, "Virtual Block RAID 1" is the newly created RAID. Double click it to start recovery.
Generated by ReclaiMe Free RAID Recovery build 889, www.FreeRaidRecovery.com
-------------------------------------------------------
Notice that the order in which you load drive images is not sequential, nor is it when you add the images to the Virtual Block RAID. Perform the steps as instructed in the order it advises.
Heres an example what youre likely to have:
-------------------------------------------------------
These instructions are provided for R-Studio version 5.1
1. Launch R-Studio
2. On the toolbar, click "Open image". Enter "S:ST2000DM001-9YN164CC4C-Disk3.dsk" as the file name, click "Open"
3. On the toolbar, click "Open image". Enter "S:ST2000DM001-9YN164CC4C-Disk1.dsk" as the file name, click "Open"
4. On the toolbar, click "Open image". Enter "S:ST2000DM001-9YN164CC4C-Disk2.dsk" as the file name, click "Open"
5. On the toolbar, click "Create Virtual RAID". Then, select "Create Virtual Block RAID" from the dropdown menu.
6. Right click the disk list on the right, select "Add S:ST2000DM001-9YN164CC4C-Disk3.dsk" from the pop-up menu.
7. Right click the disk list on the right, select "Add S:ST2000DM001-9YN164CC4C-Disk1.dsk" from the pop-up menu.
8. Right click the disk list on the right, select "Add S:ST2000DM001-9YN164CC4C-Disk2.dsk" from the pop-up menu.
9. On the right side of the R-Studio window, set "RAID type" to "RAID5".
10. Below that, set "Block size" to "64 KB".
11. Below that, set "Block order" to "Left Asynchronous".
12. In the "Parents" table, enter "0 Sectors" as "Offset" in all rows.
13. Below the RAID diagram, click "Apply".
14. On the left panel, "Virtual Block RAID 1" is the newly created RAID. Double click it to start recovery.
Generated by ReclaiMe Free RAID Recovery build 889, www.FreeRaidRecovery.com
-------------------------------------------------------
Notice that the order in which you load drive images is not sequential, nor is it when you add the images to the Virtual Block RAID. Perform the steps as instructed in the order it advises.
Also, the last step (14) is slightly misleading. Double-click on the "Basic data partition" listed beneath the root Virtual Block RAID (rather than the "Virtual Block RAID 1" itself), and that will begin recovery.
The process of mapping the Virtual Block RAID is quite fast in comparison to what youve done so far, just a few minutes after beginning youll be presented with a data recovery screen that lists all the folders/files that it could find.
In the R-Studio "File View" window, the folder list on the left, expand the Basic Data Partition, expand the Root.
This lists all the folders/files that it could find. Hopefully for you, it lists a lot.. maybe even everything!
Time to test a single file recovery:
- navigate your folder list and find a file youd really like but that isnt too big,
- select it by ticking the checkbox beside it
- click the "Recover Marked" icon up the top and follow the prompts as to where youd like to save the file.
Sometimes recovering files can take some time. For me I recovered about 1.5TB per day across the network, but it could differ for you.
Test the recovered file - if its complete and satisfactory, make sure youve saved the instructions from ReclaiMe on how to set up the Virtual Block RAID for R-Studio.
This lists all the folders/files that it could find. Hopefully for you, it lists a lot.. maybe even everything!
Time to test a single file recovery:
- navigate your folder list and find a file youd really like but that isnt too big,
- select it by ticking the checkbox beside it
- click the "Recover Marked" icon up the top and follow the prompts as to where youd like to save the file.
Sometimes recovering files can take some time. For me I recovered about 1.5TB per day across the network, but it could differ for you.
Test the recovered file - if its complete and satisfactory, make sure youve saved the instructions from ReclaiMe on how to set up the Virtual Block RAID for R-Studio.
If successful, its time for you to purchase R-Studio Network Edition.
store: https://secure.r-tt.com/cgi-bin/Store?id=1
store: https://secure.r-tt.com/cgi-bin/Store?id=1
Its also time for some semi-drastic, but highly recommended action....
Youre ready to recover your data from the NAS to your PC, so youll need your disks back in your PC.
So to start off, close everything and shut down cleanly.
At this stage you should reconsider using a RAID 5 - it is inherently fragile for current drives (read up on some of Spiceworks SAMs posts on this). Where possible grab yourself an even number of disks, buy another one if you have an odd amount, and rebuild your RAID as a RAID 10.
So, take all your disks to the original PC, plug them all back (I do it in order that I took them out, but its of no consequence now), and start er up.
Jump into your RAID config and remove all existing RAID settings and create a new RAID 10 with all drives. RAID 10 is really the way to go. Its highly recommended.
This will destroy all data on your disks so just in case, keep your NAS running to minimise risk of corruption on restarts.
Also, if youve been using FakeRAID (RAID run by the motherboard controller) consider getting yourself a proper RAID card and running your drives from there. If the controller goes on the fritz, you could be paddling without a .. paddle ..
Wait until the new RAID 10 is configured and initialised and boot into Windows.
Following Step 7, get back into R-Studio and rebuild the Virtual Block RAID so that you can see all your files again.
Restore at will to your PC, back to whence they came.
Now that you have all the data you want back, time to do some housecleaning.
If you have the space, perform a backup now. If you need, you can delete the images of your disks off the NAS first, but only if absolutely necessary and youre confident that you wont lose anything.
Get a backup system in place, preferably automated. That means if you lose a RAID again its of no consequence due to having recent backups. Check your backups often to ensure theyre being taken successfully.
You maybe used to think you didnt need backups. I hope youve learned this is not the case.
So, in the wise words of every moderator in Spiceworks, "Backup, backup, backup"
"And ... backup"
"And ... backup"
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RAID 1E Recovery
RAID 1E Recovery
RAID 1E Recovery
There are several subtypes of RAID 1E: near, far, and interleaved (see the RAID 1E diagrams). Regardless of the subtype, the RAID 1E metadata includes number of member disks, disk order, block size, and start offset on the disks. ReclaiMe Free RAID Recovery can detect RAID1E far parameters automatically. However, first you need to turn your RAID 1E to RAID 0 by truncating a half of the array using HPA and then recover the array as described below.
RAID 1E recovery with software
Before you start RAID 1E recovery consider creating disk image files (sector-by-sector copy of the disk content) if you suspect that one or several member disks are physically damaged.
- Download and start ReclaiMe Free RAID Recovery software.
- Select all the availbale RAID 1E member disks or disk image files. You can create or load disk image files using Disks button. Note that ReclaiMe Free RAID Recovery can only recover a RAID 1E with all disks present.
- Click Start RAID 0.
- Wait until ReclaiMe Free RAID Recovery detects the RAID 1E configuration.
- The restored RAID 1E configuration parameters will be displayed and then you can select any of the offered output options to finish recovery:
- Run ReclaiMe to recover data. Selecting this option you launch ReclaiMe data recovery software which will investigate filesystem structure and recover files and folders based on the restored RAID 1E configuration.
- Save layout to file (RAID XML). The recovered RAID 1E configuration parameters will be written to the file in XML format. This file can then be opened in ReclaiMe data recovery software to recover data off the array.
- Create the array image file, for later use with some other data recovery software, if you suspect there is a filesystem damage as well.
- Write array to disk, so that you can just plug it to the system and access the data. In some cases, however, the partition table has to be reconstructed before data can be accessed.
- Use with other data recovery software. This option allows you to transfer the recovered RAID1E configuration to most common data recovery tools. Note that the transferring instructions useRAID0 layout rather than RAID1E.
Alternative RAID 1E recovery options
Instead of using HPA to reduce RAID1E far member disks, you can create regions on the disks in professional data recovery software like ReclaiMe Pro and then try different recovery options.
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How to recover RAID
How to recover RAID
Before you start your RAID recovery
Consider the following:
- If one of the member disks of RAID 5, RAID 6, RAID 1E, RAID 5E or RAID 0+1 is physically damaged (produces unusual sounds, e.g. clicking or repeated spin-up and spin-down sounds), dont use this disk for recovery.
- If you cannot avoid using a physically damaged disk, say, for RAID 0 recovery, try to create the disk image file - use Create disk image under Disks on the toolbar in ReclaiMe Free RAID Recovery software.
- If you have a hardware RAID, you should
- Clearly label the member disks, the cables, and the controller ports, so that the original setup can be reassembled if need be.
- Disconnect the array member disks from the RAID controller and then attach them as separate/standalone disks to a non-RAID controller. ReclaiMe Free RAID Recovey needs to access the disks separately to be able to reconstruct RAID parameters.
- If you plan to recover data once the RAID parameters are restored, prepare a free disk space equal to the amount of data which you are going to recover.
How to recover RAID
- Download, install, and launch ReclaiMe Free RAID Recovery software.
- If it is needed, open or create disk image files of the member disks using the Disksbutton.
- Decide on the type of your array
- For RAID 0 select a minimum of two devices from the list and click Start RAID 0.
- For RAID 5, select all the available member disks and click Start RAID 5. Minimum of two disks is required. ReclaiMe Free RAID Recovery software can recoverRAID 5 with one disk missing.
- For RAID 0+1, 1+0, RAID 5E or RAID 6, select all the available member disks and pick the appropriate RAID type under Other RAIDs.
- Wait until the program completes detecting the parameters. It can take from a couple of minutes to several hours (learn why). The process completes when either Scan progress or Confidence is completely filled. Note that Scan progress always grows whileConfidence may decrease.
- At the step all the parameters have been already restored. Then you can select:
- Run ReclaiMe to recover data. If ReclaiMe File Recovery software has been already installed on the computer, then it is launched in RAID recovery mode and displays the partitions on the array. If you do not have ReclaiMe, you will be offered to download ReclaiMe File Recovery software.
- Save layout to the XML file. Save the recovered array parameters to the file inXML format. Note that you can open this file in ReclaiMe File Recovery software and start to recover data off the array using ReclaiMe RAID recovery mode.
- Use with other data recovery software. Provides step-by-step instructions on how to transfer the recovered parameters to certain well-known data recovery tools. Note that the instructions are created for each particular case of RAID and you should follow them exactly. Should the need arise, the instructions can be copied to the clipboard using Copy to the clipboard button.
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Thursday, December 1, 2016
What is RAID 0 General Information
What is RAID 0 General Information
What is RAID 0
raid0What is RAID 0
What is RAID 0We published an article about RAID 5: "How RAID 5 work? Shorter and
easier to interpret than ever" - and now is the time for a full series. We will try to show you
, in a few words, and interpretation of the shortest record levels of RAID - 0, 1, 1 + 0, 0 + 1, 2, 3, 4, 6
and matrix. Now is the time for RAID 0 - take a look ...
What is RAID 0
We can describe RAID 0 as the connection of the two (or more) physical disks - so as to look like a
logical drive and one engine. In such a case, and ability are all equal to the number of times the disk
in the "smaller" ones ability. ie- if you have two hard drives - 250GB 500GB and, and the size of the
array will be equal to 500 GB.
RAID 0 is called also "bar" or "stripping size" group. This is because it smells data (chart) between
tablets - without symmetry to repeat information. In other words, RAID 0 does not provide data
redundancy. Things, the settlement of data between disks leads to a significant acceleration in
the read and write operations - because of these parallel operations on all disks in the array.
Pros and Cons
The ability of the full group as a whole. Through the implementation of such a solution, it is also
possible to increase the speed of reading and writing (but only compared with one disc).
When we talk about RAID 0, its also necessary to write about the negatives. The first is the issue
of safety data. Is not designed like this method to prevent data loss. This means that a single disk
failure may cause loss of all data contained in the matrix. Moreover, the data can be restored can
be difficult because they are distributed on all disks. It is also impossible to retrieve the "blueprint"
of data. Even when you use a special (and expensive) tools, data recovery can be incomplete and corrupt.
The second thing is the ability. Used even if two disks - 100 GB and 1 TB - will store set equal to
200GB. So the use of disks with different capacities is uneconomical because of the inability to
use the full storage potential.
RAID 0 is useful when
Because the only RAID interest 0 is the write / read speed, we can at one point only the rational
use of it - to build a cheap and effective matrices and solutions use based on the RAID 1 + 0 or RAID 0 + 1.
Check it out for RAID 1 and RAID 0 + 1 and RAID 1 + 0 solutions.
raid0What is RAID 0
What is RAID 0We published an article about RAID 5: "How RAID 5 work? Shorter and
easier to interpret than ever" - and now is the time for a full series. We will try to show you
, in a few words, and interpretation of the shortest record levels of RAID - 0, 1, 1 + 0, 0 + 1, 2, 3, 4, 6
and matrix. Now is the time for RAID 0 - take a look ...
What is RAID 0
We can describe RAID 0 as the connection of the two (or more) physical disks - so as to look like a
logical drive and one engine. In such a case, and ability are all equal to the number of times the disk
in the "smaller" ones ability. ie- if you have two hard drives - 250GB 500GB and, and the size of the
array will be equal to 500 GB.
RAID 0 is called also "bar" or "stripping size" group. This is because it smells data (chart) between
tablets - without symmetry to repeat information. In other words, RAID 0 does not provide data
redundancy. Things, the settlement of data between disks leads to a significant acceleration in
the read and write operations - because of these parallel operations on all disks in the array.
Pros and Cons
The ability of the full group as a whole. Through the implementation of such a solution, it is also
possible to increase the speed of reading and writing (but only compared with one disc).
When we talk about RAID 0, its also necessary to write about the negatives. The first is the issue
of safety data. Is not designed like this method to prevent data loss. This means that a single disk
failure may cause loss of all data contained in the matrix. Moreover, the data can be restored can
be difficult because they are distributed on all disks. It is also impossible to retrieve the "blueprint"
of data. Even when you use a special (and expensive) tools, data recovery can be incomplete and corrupt.
The second thing is the ability. Used even if two disks - 100 GB and 1 TB - will store set equal to
200GB. So the use of disks with different capacities is uneconomical because of the inability to
use the full storage potential.
RAID 0 is useful when
Because the only RAID interest 0 is the write / read speed, we can at one point only the rational
use of it - to build a cheap and effective matrices and solutions use based on the RAID 1 + 0 or RAID 0 + 1.
Check it out for RAID 1 and RAID 0 + 1 and RAID 1 + 0 solutions.
Go to link download
Monday, November 14, 2016
RAID 2 RAID 3 RAID 4 What are the characteristics and how does it work And its history
RAID 2 RAID 3 RAID 4 What are the characteristics and how does it work And its history
RAID 2, RAID 3, RAID 4 – what it is, how it works? The history lesson
After RAID 0 and RAID 1 (with RAID 1+0 and RAID 0+1) it is time for RAID 2, 3 and 4. Here we present a small description of the mentioned levels. We hope it will outline a picture of the functionality of these solutions. Although the article is a kind of history lesson – these solutions are no longer used – it is good to be aware of the origins of modern storage technologies.
RAID 2 – the bit-level striping with dedicated Hamming-code parity
In the case of RAID 2 all data are stripped (to the bit levels – not block). Each bit is written on a different drive/stripe. Such a solution requires the use of Hamming code for error correction.
Hamming code is a linear error-correcting code named after its inventor, Richard Hamming. Hamming codes can detect up to d – 1 bit errors, and correct (d – 1) / 2 bit errors, where d is the minimum hamming distance between all pairs in the code words; thus, reliable communication is possible when the Hamming distance between the transmitted and received bit patterns is less than or equal to d. By contrast, the simple parity code cannot correct errors, and can detect only an odd number of errors.
source
The number of discs in RAID 2 used to store information is equal to the logarithm of the number of discs that are protecting the mentioned data. All disks in RAID 2 work as one disk which has a capacity equal to the common capacity of all disks used to store data.
RAID 2
While RAID 2 is being used it is important to synchronize all disks. Such a solution requires that the controller, which makes disks, will spin at the same angular orientation – in other way the index will not be reached at the same time. Disintegration will lead to total uselessness of drives in array.
Such a requirement is not the only drawback. Also the need for long Hamming code generation may prove to be problematic by slowing the whole system down.
The mode of RAID 2 action may be hard to understand. The need for using Hamming code, special controllers for disks – it makes RAID 2 a not very popular solution. But if we think about it in a less pragmatic way, it may prove to be very interesting – mainly due to its modus operandi. It introduces many more complex solutions than RAID 0 and RAID 1. While everything works well, RAID 2 proves to be quite a good solution in area of data security. In case of HDD failure – no matter if it was the disk with data or the Hamming code – any part of the array may be reconstructed by the other disks used.
While it is interesting and it has its advantages, we have not heard about any commercial implementations of RAID 2. Solutions based on it were used only in the initial phase of RAID systems usage – before disks were equipped with their own correction code. Modern HDDs use various correction and optymalising algorithms. That is why the Hamming system has started to be less interesting in the area of professional usage and it is no longer implemented in modern controllers.
RAID 3 – another rare one in practice
RAID 3 works as RAID 0 does – it uses byte-level stripping – but it also uses an additional disk in the array. It is used to store checksums and it supports a special processor in parity codes calculating – so we may call it “the parity disk”.
RAID 3
In RAID 3, configuration data are divided into individual bytes and then saved on a disk. Parity byte is determined for each row of data and saved on the mentioned “parity disk”. In case of failure it allows to recover data by an appropriate calculation of the remaining bytes and parity bytes that correspond with them.
Although RAID 3 is rarely used in practice, it is worth pointing out its advantages. First of all is its resistance to damage of one disk in the arrangement. Secondly, high read speed. Unfortunately, it also has a couple of drawbacks.
The read speed is more than satisfactory but write speed is on the contrary – the reason being the necessity of checksums calculating (even RAID hardware controllers cannot solve this problem). She second disadvantage is a matter of disk failure. When it happens, the whole system will work much slower. What is more, although RAID 3 is resistant to breakdown (in case of failure of one disk in the array), replacing a damaged disk is very costly. A third problem is the disk used for calculating checksums – it is usually the bottleneck in the performance of the entire array.
As can be easily seen, RAID 3 is not a good, reliable or cheap solution. Therefore, as it was mentioned earlier, its use is rare in practice. Systems based on RAID 3 are mostly purposed for implementations where a small number of users refer to the very large files.
RAID 4 – smells like RAID 3 and 5
RAID 4 is very similar to RAID 3. The main difference is the way of sharing data. They are divided in to blocks (16, 32, 64 lub 128 kB) and written on disk s – similar to RAID 0. For each row of written data, any recorded block is written on a parity disk. In short this means that RAID 4 does not strip data at block levels but it uses byte levels for striping (block-level striping with a dedicated parity disk).
There are also similarities in relation to RAID 5, but it confines all parity data to a single drive. RAID 4 does not use distributed parity.
RAID 4
RAID 4 requires at least three disks for complete implementation and configuration. What is more, it also needs hardware support for parity calculations. This makes it possible to recover data by the appropriate mathematical operations.
If we asked: what is RAID 4 for? we would point out one particular need. Such a solution will work very well in the case of really large files – when sequential read and write data process is used. Using RAID 4 for small portions of data would be not a good idea. The reason is the need to carry out modifications of parity blocks for each I/O session. The need for continuous repeating of such an operation would cause large losses of time and slow down a whole system.
RAID 3 and RAID 4 solutions were replaced by RAID 5. You can read about it in an article by Janusz B?k: “How does RAID 5 work? The Shortest and Easiest explanation ever!”
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Saturday, November 12, 2016
RAID 5E layout
RAID 5E layout
RAID 5E layout
RAID 5E (RAID 5 Enhanced) array is one of the RAID 5 variations. RAID 5E differs from normal RAID 5 in having integrated spare space to rebuild the array immediately when one of the member disks fails. The size of this additional space equals the size of one member disk. Data is written on RAID 5E in the following way:
The main RAID 5E advantage is the performance increase both write and read speeds as compared to RAID 5 with a dedicated hot spare drive. The significant disadvantage is the complexity of rebuild in case of a member disk failure. As of now, RAID 5E can be created only using a standalone controller, say, an IBM ServeRAID controller.
RAID 5E Recovery
For RAID 5E, recovery of array parameters is exactly the same as for a regular RAID 5 (see the detailed instruction on the RAID 5 recovery page). You can recover RAID 5E configuration using ReclaiMe Free RAID Recovery. There will be extra zero-filled space written after the array content in the image file or when the array is written directly to the disk. Typically, this does not have any side effects on recovery.
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Tuesday, November 8, 2016
RAID 6 Recovery
RAID 6 Recovery
RAID 6 Recovery
RAID 6 parameters
RAID 6 layout utilizes two different parity functions which helps a RAID 6 array survive up to double disk failure. Despite of the fact that RAID6 is perceived to be more reliable than a RAID 5, the probability of a controller failure is the same. So if your RAID6 fails, this will most likely be due to a controller failure. To recover a RAID6 from a controller failure, you need to know or recover the following parameters:
- number of member disks
- disk order and which disk was the first in the array
- block size
- start offset on the member disks
- positions of each parity function
- rotation of parity functions
- algorithm used to calculate the second parity function
- pattern of parity functions
You should know all these parameters to reconstuct RAID 6 successfully. Our software ReclaiMe Free RAID Recovery (download) can recover RAID6 configuration automatically. See the step-by-step RAID Recovery instructions.
RAID 6 variations
RAID 6 is significantly more complex than RAID 5.
- The first parity function (XOR, denoted as P on the diagrams) naturally comes from RAID5. However, there is no widely accepted standard for the second parity function (Q). Typically, a Reed-Solomon code or some variation thereof is used.
- Reed-Solomon code depends on the order in which input is provided. This produces four more variations: left-to-right or right-to-left and if P or Q is calculated first.
- There are several variations of layout accomodating two parity functions.
Missing disk limitations
Maximum of one missing disk is allowed. Although RAID 6 should be recoverable with two disks missing, the implementation of ReclaiMe Free RAID Recovery cannot work with two disks missing.
With Promise hardware RAID 6, no missing disks are allowed at all (as of build 381).
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