Showing posts with label work. Show all posts
Showing posts with label work. Show all posts
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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Friday, October 21, 2016
How to Effectively Work Cloud Computing
How to Effectively Work Cloud Computing
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How to Effectively Work Cloud Computing |
At this server computer all data are stored including applications, installed on the server computer linked so that users can use any time when the Internet can be linked to a computer server.
For users who access the server storing the data or run a program, it takes the user must login and then the user can use cloud server resources to run a program without installing it on your own computer and also for storing data.
User runs an application provides several commands on the application, then the commands in the input by the user will be sent to the server across the Internet then processed / response by the server and then displays the results, the data from the results of this process are stored in the computer server, so every time the user wants to open and see the data that has been saved, the data will still be available on the cloud servers.
For example :
The use of email users do not need to download and install the email application on his computer, just simply connect to the Internet, the user is able to use the email application on the cloud server.
Problem Of Cloud Computing
Data SecurityData security issues still be considered for the use of cloud systems, users of computers connected to the Internet network access server cloud, perhaps the intruders or call into the server computer cracker steal your data, then choose the server cloud that you value quite safe and have integrity the good one.
The Privacy
Privacy or data, of even the system used in implementing cloud server data encryption, but still allows the data stored in the cloud server readable by certain parties.
Prone intruders
Data security in the cloud computer can be a problem, such as the hacking of data, intruders like viruses / malware to the cloud server and be a problem if a security system that has been implemented by the server administrator has, it might happen.
Server Experiencing Off
The server experienced downtime caused by various measures such as high data capacity in the loading at the same time so that the server resources to be slow.
The server may be down due to unstable internet network server computer.
The Advantages of Using Cloud Computing
Efficient use of memoryThe use of cloud computing infrastructure such as storage prepare various software no longer need to prepare a large capacity hard drive on his computer, the user simply by using the server.
The flexibility
Because the server is an Internet-based cloud service users to access at any time if it is connected to the internet cloud computing services make the user feel more flexible.
Fully scalable
Providing cloud services and offers data storage according to user request, the user easier management of data to be stored in the cloud server.
The disadvantage Using Cloud Computing
The user must be connected to the InternetRequire users to connect to the internet in order to access the server the user must provide internet network devices.
Cost for cloud server provider
Even smaller capacity than using multiple applications in the cloud computers with small capacity if instead you use the great resource of the server computer server cloud service providers pay your usage, it is reasonable.
Similarly, regarding cloud computing to take advantage of cloud computing technology using cloud-based applications to secure data that we consider important so that if there is damage such as damage to the stored data is still safe.
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Monday, October 10, 2016
How RAID 5 work Shorter and easier to interpret than ever!
How RAID 5 work Shorter and easier to interpret than ever!
How RAID 5 work? Shorter and easier to interpret than ever!
We all have to lack of time to study the long and complex information about RAID theories, but you
may be interested in how RAID 5 works. We made it easy for you by providing explain shorter and
easier than ever before.
RAID 5 - How does it work?
First we need to remind you of the definition of XOR:
XOR result of the function is equal to 1 if all the arguments are different.
XOR (0, 1) = 1
XOR (1, 0) = 1
XOR output function is equal to 0 if all the arguments are the same.
XOR (0, 0) = 0
XOR (1, 1) = 0
Now lets assume we have 3 drives with the following bits:
| 101 | 010 | 011 |
I daresay XOR that data and put it on the CD 4
XOR (101, 010, 011) = 100 (XOR (101010) = 111, and XOR (111, 011) = 100
Therefore, the data on the four engines looks like this below:
| 101 | 010 | 011 | 100 |
Now lets see how it works XOR MAGIC. Lets assume the second drive failed. When we calculate
XOR all the remaining data will be present from the engine missing.
| 101 | 010 | 011 | 100 |
XOR (101, 011, 100) = 010
You can check the other drives were missing, and will XOR of the remaining data always give you
exactly the data from your missing disk.
| 101 | 010 | 011 | 100 |
XOR (101, 010, 100) = 011
What works for 3-bit and 4 drives only, and works for any number of parts and any number of drives.
RAID 5 real has the most common form of 64K stripe size (65536 * 8 = 524288 bit)
Thus, the real XOR engine only needs to deal with the 524288-bit 3-bit and not, as in our practice.
This is the reason that RAID 5 needs to be very effective XOR engine in order to calculate it quickly.
Even when you add one drive for parity will be able to re-build the lost data in the event of a drive failure.
In our example we have explained RAID 4, where a dedicated parity drive. RAID 5 will parities
distributed evenly among all the drives. Provides parity distributed a slight increase in performance,
but the magic XOR is the same.
To learn more about RAID 5 please go to the Wikipedia article.
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