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.
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