Server Raid 5 data recovery case
The case shared this time is a raid disk array in a server. There are 12 disks in the disk array, and the capacity of a single disk is 500G. ext3 file system, the system platform is Linux platform. The two hard disks in Raid No. 2 and No. 6 reported a yellow light. After checking, the management performed a forced online operation of No. 6 disk. After the forced go online, it was found that most of the directories could not be opened, and some of the directories that could be opened appeared in some directories. File loss situation. The customer contacted the North Asia Data Recovery Center for data recovery of the raid disk array. 
1 .Firstly, analyze the original raid structure, remove the forced-on-line No. 6 disk, add the No. 2 disk, and build the raid platform through the virtual environment.
2. Then use the software to extract auxiliary data. After extracting the data, an irregular bad track was found on the No. 2 disk.
3. We chose a commonly used mirroring tool to perform a complete mirroring of the No. 2 hard disk, and more than 90% of the bad sectors were successfully read.
4. Add the completed image data to the virtual raid environment and extract the data again. More than 99% of the data is completely restored.
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Principle of Raid 5 data recovery algorithm****
To understand the principle of raid 5 data recovery, you must first understand raid5, the independent disk structure of distributed parity (that is, What we call raid 5) Data recovery has a concept of “parity” that needs to be understood. We can simply understand it as the “exclusive OR operation” in binary operations, and the commonly used symbol is xor. The rule of operation is that if the two values are the same, the result is 0, and if the two results are different, the result is 1.
For example, if 0101 xor 0010 is calculated according to the above algorithm, the first digit of both is 0, and the two are the same, the result is 0; the second, third, and fourth digits are different, the result is 1, so the final result It is 0111, expressed by the formula: 0101 xor 0010 = 0111, so if one of them is missing in a xor b=c, we can calculate from other data. This is all the secrets of raid5 data recovery. After understanding this secret Raid 5 data loss is not a problem for you to recover the data yourself.