Shulou(Shulou.com)06/02 Report--

Server Data Recovery Case 1:

A DELL server disk array crash in a research institute, built-in RAID 5 array built with 15 1TB hard disks. One hard disk was offline at first. During the process of replacing a new hard disk for synchronization, the indicator light of the second hard disk gave an alarm, synchronization failed, and the array could not work normally.

Server data recovery detection:

The first disk that went offline was extremely slow to access, the second disk that went offline had a few bad sectors, and the others had no obvious physical problems.

Server Quality Logic Status:

The entire array consists of only one volume group, which occupies all of the array space, and which has only one XFS bare partition starting at sector 0.

Develop a server data recovery plan:

RAID5 array architecture is designed to support error redundancy for only one disk, and the array will not function properly when the second disk goes offline. According to the user description, the crash of the entire array was mainly caused by the second disk. So the processing of the second disk is the key to this recovery

Server data recovery process:

1. Backup all hard disks as read-only images, backup the second offline hard disk separately, and skip bad sectors during backup.

2. Conduct XOR test on 15 hard disk image files, all pass without obvious error.

3. Calculate the data of the damaged sector location of the second hard disk and write it to the image file.

4. Analyze the original RAID composition structure during the backup process and build a virtual RAID environment.

Verify that the RAID structure is correct.

6. Backup the image of the second disk to the new hard disk, force it online, replace the first disk, and synchronize it. (Note: backup all hard disks before operation)

7. Copy the data.

Server Data Recovery Conclusion:

Because the XOR test completely passes, it indicates that no new data has been written or the structure has changed since the storage failed.

So you can calculate the data corresponding to the location of the bad hard disk based on several other good hard disks.

After the restoration, the directory structure is complete and all important documents are intact. FSCK does not have any error prompt, the customer recognizes the recovered data, and the recovery is successful.

Server Data Recovery Case 2:

A company's P4500 server raid failure, forced online operation after the raid is still unavailable, the user stores a total of three groups of raid, two volumes, 12 physical hard disks. Details are as follows:

The first step of server data recovery: detect the physical hard disk, hard disk failure, and then all the disks in the server for a full mirror and image file analysis. The bottom RAID is an HP double cycle RAID 5, the first RAID is OK. The second RAID group is also RAID 5, so it is certain that the number of lost disks in the second RAID group is at least 2.

Server data recovery Step 2: Use exhaustive plus verification method to analyze the earliest disk after the line kicked out, reorganization raid.

Finally, mount the generated data to the HP-P4500 server along with the first set of intact RAID. Then start the server, the upper volume is available, check that the latest file is normal, and the data recovery is successful.

Server Data Recovery Case Summary:

Due to the continuous advancement of technology, different models of servers have different ways to deal with RAID 5 failures.

Nowadays, the network topology structure of large-scale application programs generally adopts C/S structure or B/S structure, and at least one server with large database is required to be placed in the central computer room. Based on the consideration of server security and reliability, RAID(Redundant Array of Inexpensive Disks) is usually used for disk redundancy backup. RAID 5 array level is parity disk array without independent check disk. It adopts data blocking and independent access technology, and can process multiple access requests on the same disk in parallel, while allowing any hard disk in the array to fail.

In practical application, due to some unavoidable objective reasons, some array failures may occur. The most common condition is that the hard disk goes offline by itself, the connection status is displayed as DDD(Defected Disk Drive), and the hard disk has a physical failure or logical failure. If it is a physical failure, only hard disk replacement can be carried out; if it is a logical failure, targeted technical repair can be carried out to restore the online state of the hard disk, continue to maintain the striping distribution state of the hard disk data in its original array, and continue the consistency of the data storage system.

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