Shulou(Shulou.com)06/03 Report--

[user unit]

A branch of China Unicom

[description of data recovery failure]

SUN optical fiber storage system, the central storage is a RAID6 composed of six 300G hard disks, divided into several LUN,MAP to different business servers, the server runs the SUN SOLARIS operating system.

In the normal working state, users need to add new applications, so an IBM server is added, and then a LUN in storage is mapped to the new IBM server online. Unexpectedly, the mapped volume was originally MAP to a LUN on the SOLARIS production system. Because it was not found in time, the LUN has been partially initialized on the IBM server (the operation is unknown), and then an error was reported on the disk on SOLARIS. A problem was found after reboot, and the volume could not be mounted.

After the SUN engineer tests, execute fsck, and the file system can be hung up after completion, but a lot of data is lost or the size becomes zero, especially the latest data is seriously corrupted.

[data recovery failure analysis]

This kind of failure is common in SAN environment, but most of it is caused by human carelessness, and so is this fault. Normally, the LUN allocated by SAN is in exclusive mode. If it is controlled by several operating systems at the same time, it can easily lead to non-mutual exclusion of write operations and file system consistency errors.

If you want to recover this part of the data, you need to go deep into the file system to examine the destruction of its structures. In this example, because the file system uses UFS, for any file that needs to be recovered, priority is given to whether the directory information, node and data area are normal. If the above three structures are normal, the data can be fully restored. However, in most cases, the INODE will be cleared after fsck, and even if you leave directory information, it will not be able to correspond to the data one by one. In this case, you can only refer to the internal format of the file for type recovery.

[data recovery process]

1. Make a full backup of the failed volume. Since there is no fault in RAID, make a dd backup of the original LUN directly in the SOLARIS environment.

2. Analyze the file system in the backup to make sure that the inode of the files to be restored has been cleared and cannot be restored. We have to deal with it according to the file type.

3. Based on the analysis of the specific files that users need to recover, it is found that the index files using vfs document system have strong type characteristics, and the files contain directory information.

4. According to the index structure characteristics of the official document system, the writing program is extracted and renamed according to the features.

5. Restore the data file by type, and then the user manually reorganizes the data file according to the index file.

[conclusion of data recovery]

After 24 hours, 99% of the directory index files were successfully restored, most of the data files were successfully restored, and the rest of the files that could not be recovered were destroyed, and users collected them from other departments according to the directory index files.

In conclusion, the user recognizes that the data recovery is successful.

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