Raid Data Recovery

RAID arrays are usually used in servers for the purpose of increasing reliability of stored information or disk system performance. There are both hardware and software RAID arrays.

High reliability of storing data in RAID arrays is provided by means of data redundancy and implies fault tolerance towards failure of particular disks from a RAID array.

Increase in data access speed is possible only in some levels of RAID array and can be implemented by means of simultaneous execution of similar operations on different disks from array.

There are different levels of such arrays, for instance, RAID 0, RAID 5, RAID 10 and so on.

Unfortunately, regardless of all measures directed on improvement in RAID array data storage reliability, they fail to guarantee complete integrity of information. There are a number of reasons, which can lead to destruction of data. In general such reasons are related either to human element or to failures of hardware and software.

Let’s examine the ways of data recovery from RAID arrays of different levels in detail:

RAID 1 data recovery

  1. First, analysis of destruction over all drives is carried out. Next, each drive is copied to an image file excluding defects. After reading all stable portions of data, problem portions are read, and finally the copy most relevant to the original is made.
  2. Merging of two copies with regard to defects (subject to data relevancy to the original) is carried out.
  3. If present, logical impairments of file system are fixed, and result is copied to another media.

RAID 0 data recovery

  1. Analysis of destruction over all drives is carried out. Next, each drive is copied to an image file excluding defects. After reading all stable portions of data, problem portions are read.
  2. Interlace block size is determined.
  3. Offset for each drive and the interlace order are determined.
  4. Result image is created, while fixing impairments in file system if needed. Then it is copied to another media.

RAID 5 data recovery

  1. Analysis of destruction over all drives is carried out. Next, each drive is copied to an image file excluding defects. After reading all stable portions of data, problem portions are read.
  2. Interlace block size is determined.
  3. Offset for each drive, parity interlace block order, and the data interlace order are determined. If only one drive from array fails, it is not necessary to recover data from it, since the data from missing disk will be restored based on parity block and the data on the rest of drives.
  4. Result image is created, while fixing impairments in file system if needed. Then it is copied to another media.

RAID 6 data recovery

  1. Analysis of destruction over all drives is carried out. Next, each drive is copied to an image file excluding defects. After reading all stable portions of data, problem portions are read.
  2. Interlace block size is determined.
  3. Offset for each drive, parity interlace block order, and the data interlace order are determined. If only two drives from array fail, it is not necessary to recover data from those, since the data from missing disks will be restored based on parity block and the data on the rest of drives.
  4. Result image is created, while fixing impairments in file system if needed. Then it is copied to another media.

RAID 10 data recovery is similar to RAID 0 data recovery with only difference that it may be necessary to determine relevancy of copies against originals.

RAID 50 data recovery is similar to RAID 5 data recovery with a difference that it will be necessary to recover two RAID 5 arrays and merge them into single RAID 0 image afterwards.

RAID 60 data recovery is similar to RAID 6 data recovery with a difference that it will be necessary to recover two RAID 6 arrays and merge them into single RAID 0 image afterwards. Matrix RAID data recovery is basically recovery process of one or more RAID 0, 1, 5 arrays depending on actual configuration.