The principle of the server Raid 5 disk array algorithm

The independent disk structure of distributed parity (also called raid 5) data recovery has a “parity” concept Need to understand. 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.

Server What to do after disk array failure: (Other raid arrays including raid5 disk arrays are similar)

Don’t blindly go online
Required when the Offline indicator prompts The user replaces a good identical hard disk and re-verifies the algorithm. Among the multiple hard disks that RAID5 disk arrays are likely to purchase at the same time, a few have been unstable. The Offline prompt of the server may not be the most accurate, and it often misreports (there are also factors of hard disk instability) or misses other hard disks that also have hidden dangers. The hard disk needs to perform a lot of read and write operations during the forced online process. 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 being forced to go online, so as to be more secure.

Protect the first site
For manufacturers, hardware equipment is the main purpose of after-sales service. Therefore, they often sacrifice data to ensure that the hardware equipment is in good condition as soon as possible. According to the engineer in charge of the data recovery center, cases of complete data destruction due to repairs by the after-sales service engineers of the ××× dealers occur almost every week. After all, after-sales service engineers are basically inclined to hardware, and RAID data recovery is mainly based on software operations. In addition, even simple verification operations may bring inconvenience to later data recovery. When the raid hard disk is damaged beyond the fault tolerance, the mirror image of the damaged hard disk must be completely extracted to perform the final recovery. However, if the hard disk is frequently powered on, it is easy to cause further fatigue damage to the head, and even scratch the disk. The correct way to deal with it should be to consult a professional data recovery service provider immediately.

Choose a professional data recovery center
The company size, technical level, engineer team, and reputation in the industry are all important indicators that need to be considered when choosing a data recovery service provider.

Data recovery method after the server raid disk array deletes VG by mistake:

Raid disk array data recovery case background:
The faulty raid array is in After replacing the disk, data synchronization was performed. At this time, the VG information was deleted and the data synchronization was terminated. After the operation and maintenance personnel import the backup VG information, the RAID is a new RAID array. Generally speaking, once the data is synchronized, the new raid array will be synchronized to a blank disk, and the data cannot be recovered. Fortunately, the manufacturer’s technicians turned off the data synchronization function for safety. It is this operation that saved the data, otherwise the server data will suffer irreversible damage. The customer chose the North Asia Data Recovery Center after comparing it among a number of data recovery companies in Beijing.

Raid disk array data recovery steps
1. Mirror all the disks in the server disk array individually to the secure storage of the North Asia Data Recovery Center. The original disk will no longer be operated to ensure the originality of the user’s disk.
2. Analyze the underlying structure, reconstruct the original RAID, reorganize the RAID virtually, and mirror it to the temporary storage in the North Asia Data Center.
3. Use the VMWare ESX data recovery software independently developed by North Asia Data Recovery Center: Frombyte Recovery For ESX to restore.
4. After all the data can be seen normally, the restored storage will be linked to North Asia for data recovery Verify all data on the ESXi server in the center.

Recovery method of server disk array mdisk disk offline data:

Raid disk offline process description
There are 8 sets of Mdisk in the server, one of which is Mdisk One of the hard disks failed offline. During the hot spare disk activation and replacement process, another hard disk in the same group of Mdisks also failed offline, causing the hot spare disk to fail to synchronize, and the group of Mdisks failed, causing the entire universal volume to be unusable.
Recovery method for server disk array data: 1. I mirror each disk through the mirroring software, and all subsequent data recovery work will be performed on the mirror disk, and the original disk always remains the original The status does not affect the data. The main purpose is to prevent misoperation during the data recovery process. Once the operation error will lead to the secondary destruction of the original disk data, the later data recovery will be more difficult. 2. Analyze and reorganize Mdisk, first classify the hard disks according to the Mdisk group according to part of the configuration information provided by the customer. Analyze all the hard disks in each group of Mdisks to obtain related raid information. Use professional data recovery software to perform virtual reorganization of Mdisk. 3. Analyze all Mdisks and get relevant information about the pool. Use professional data recovery software to virtually reorganize the pool. 4. Drop analysis. Due to the inherent characteristics of raid5, we know that raid5 can allow at most one member disk to be offline, which means that if one member disk fails, raid5 can still be used normally. Therefore, it can be judged that two disks failed at that time based on the previous raid failure. After analyzing the underlying data in each member disk, it is found that there are two hard disks, and the data on the front of the hard disk is exactly the same, so it is judged that one hard disk of the two disks is a hot spare disk, and the other hard disk is a faulty disk. Based on this, it can be preliminarily inferred that one of the member disks in the raid fails first. During the synchronization of the hot spare disk, the other member disk also fails, causing the raid to fail. When the raid returns to normal afterwards, because the data on the hard disk that failed first is not up to date, the data in the normal raid has some errors. 5. After analyzing the raid structure of the hard disk and the disk drop of the member disks, use professional data recovery software to complete the formation of Mdisk and pool, and generate the data in them.