# RAID array algorithm research +raid data recovery case

Source: Internet
Author: User

Principle of RAID5 Data recovery algorithm

To understand the principle of RAID5 data recovery first to know RAID5, "distributed parity of the independent disk structure" is what we call the RAID5 data recovery has a concept to understand, that is, "parity check." We can simply understand it as an "XOR operation" in binary operations, usually using an XOR identity. The rule for this operation is that if the values are the same, the result is 0, and if the results are different, the result is 1.
For example, 0101 xor 0010 is calculated according to the above operation rules, both the first digit is 0, the same, the result is 0; 第二、三、四位 has a different value, the result is 1, so the final result is 0111, expressed as: 0101 xor 0010 = 0111, so in a XOR If one of these is missing in b=c, we can extrapolate from other data, which is all the secret of RAID5 data recovery, and it's no problem to RAID5 data loss after you know the secret.

RAID5 Data Recovery case

The raid in the case requiring data recovery is built on the PowerEdge server, a total of 12 drives, a single disk capacity of 500G, the system platform for the Linux platform, ext3 file system. Raid in 1th and 4th, two hard disks reported yellow lights, management personnel after the check on the 4th plate has been forced on-line operation, forced on-line found that most of the directory can not open, there are some directories in the directory in which file loss occurs.

1. First analysis of the original RAID structure, the force on-line 4th to remove the disk, the 1th plate into the virtual environment to build a raid platform.
2. Then through the software to extract the auxiliary data, after extracting the data in the 1th plate found irregular bad way.
3. We have selected a common image tool to carry out the full image of the 1th hard drive, more than 90% of the bad word successfully read.
4. Add the good image data to the virtual RAID environment, extract the data again, and more than 99% of the data are fully recovered.

RAID array algorithm research +raid data recovery case

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