Data recovery method for data loss caused by different failures of server raid5 disk array (case)

Server Raid 5 Array Algorithm

The algorithm used by Raid5 arrays is often called "XOR", which is a mathematical operator. It applies to logical operations. The mathematical symbol for XOR is "⊕" and the computer symbol is "xor". Its algorithm is: a⊕b = (¬a ∧ b) ∨ (a ∧¬b). If the two values ​​of a and b are not the same, the XOR result is 1. If the values ​​of a and b are the same, the XOR result is 0.
XOR is also called half addition, and its algorithm is equivalent to binary addition without carry: in binary, 1 means true, 0 means false, then the XOR algorithm is: 0⊕0=0, 1⊕0= 1, 0⊕1=1, 1⊕1=0 (the same is 0, the difference is 1), these rules are the same as addition, but without carry. XOR is abbreviated as XOR, EOR, EX-OR, and there are three kinds of operators in the program: XOR, xor, ⊕. Use as follows z = x ⊕ yz = x xor y

How to recover data from Raid5 array VG deletion:

Reasons for accidental deletion of Raid5VG:
After the RAID5 array is replaced with a disk, data synchronization is performed. If the VG information is deleted at this time, the data synchronization will be aborted. In this case, the data has been synchronized, and the new array will be synchronized as a blank disk, and the data cannot be recovered. Some manufacturers choose to turn off the data synchronization function for safety reasons. At this time, a professional data recovery company can perform data recovery operations. The success rate is high

. Raid5 disk array data recovery steps

1. All disks in the server disk array are individually mirrored to the safe storage of the North Asia Data Recovery Center, and the original disks will no longer be manipulated to ensure the originality of the user disks.
2. Analyze the underlying structure, reconstruct the original RAID, virtually reorganize the RAID, and mirror it to the temporary storage in the North Asia data center again.
3. Use the VMWare ESX data recovery software independently developed by North Asia Data Recovery Center: Frombyte Recovery For ESX for recovery
4. After you can see all the data normally, hang the recovered storage on the ESXi server of the North Asia Data Recovery Center to verify all the data.

Server disk array mdisk disk offline data recovery method:

The reason for the failure of a raid disk offline describes
one or more groups of Mdisks in the server. One of the hard disks in one group of Mdisks fails and goes offline. During the activation and replacement of the hot spare disk, if another hard disk in the same group of Mdisks also fails and goes offline, it will cause The synchronization of the hot spare disk fails, and the Mdisk of the group becomes invalid, so that the entire common volume cannot be used.

Server disk array data recovery method:

1. I use the mirroring software to perform mirroring operations on each disk, and all data recovery work in the later period will be carried out on the mirrored disk. The original disk is always in its original state and does not affect the data. The main purpose is to prevent misoperation during the data recovery process. Once the operation is wrong, the original disk data will be damaged twice, and the later data recovery will be more difficult.
2. To analyze and reorganize Mdisk, first classify the hard disks according to Mdisk groups according to some configuration information provided by the customer. All hard disks in each group of Mdisks are analyzed to obtain relevant raid information. Use professional data recovery software to perform virtual reorganization of Mdisk.
3. Analyze all Mdisks to get information about the pool. Use professional data recovery software to virtually reorganize the pool.
4. Disk analysis. Due to the inherent characteristics of raid5, we know that raid5 can allow at most one member disk to be offline, that is to say, if one member disk fails, raid5 can still be used normally. Therefore, it can be judged that there were two disk failures at that time in combination with the previous raid failure.
   After analyzing the underlying data of each member disk, it is found that there are two hard disks, and the data in the front of the hard disks are exactly the same, so one of the two disks is judged as a hot spare disk and the other is a faulty disk.
   Based on this, it can be preliminarily inferred that one member disk in the raid failed first, and during the synchronization of the hot spare disk, another member disk also failed, resulting in the failure of the raid. When the raid returns to normal, the data on the hard disk that fails first is not up-to-date, so some errors occur in the data in the normal raid.
5. After analyzing the raid structure of the hard disk and the drop of member disks, use professional data recovery software to complete the formation of Mdisk and pool, and generate the data in them.

What to do after a server disk array failure: (similar to other raid arrays including raid5 disk arrays)

Do not blindly force the user to go online
when prompted by the Offline indicator, and ask the user to replace the same intact hard disk and re-calibrate the algorithm. The RAID5 disk array is likely to purchase multiple hard disks at the same time, and some of them have already appeared unstable. However, the offline prompt of the server may not be the most accurate, and it often results in false positives (there are also factors of hard disk instability) or omission of other hard disks that also have hidden dangers. During the forced online process, the hard disk needs to perform a large number of read and write operations. Once other hard disks suddenly go offline, data recovery becomes more difficult. Therefore, it is necessary to check the stability of each hard disk before forced online, so as to be more secure.

Protect the first site
For manufacturers, hardware equipment is the main purpose of after-sales service, so data is often sacrificed to ensure the integrity of hardware equipment as soon as possible. According to the engineer in charge of the data recovery center, cases where the data is completely destroyed due to repairs by after-sales service engineers of XXXX companies will happen almost every week. After all, after-sales service engineers basically prefer hardware, while RAID data recovery is mainly based on software operations. In addition, even simple verification operations may bring inconvenience to later data recovery. When the damage of the raid hard disk exceeds the fault tolerance capacity, the image of the damaged hard disk must be completely extracted for final recovery. If the hard disk is powered on frequently, it is easy to cause further fatigue damage to the magnetic head, and even scratch the platter. The correct approach should be to consult a professional data recovery service provider immediately.

Choosing a professional data recovery center
When choosing a data recovery service provider, company size, technical level, engineer team, and reputation in the industry are all important indicators to consider.