Enterprise mail server raid suddenly offline how to recover?

Source: Internet
Author: User

Enterprise mail server, stored in 146gx6 RAID5, there are millions of business users of mail, data area, only one zone, file system for ReiserFS, normal work, RAID suddenly offline, the administrator to the computer room inspection, found that there are two of disk alarm, A piece of force on the line after the discovery of the volume can not mount, so force fsck and Rebuld TREE, lasted 4 days, after completion still cannot mount. Helpless, to the data recovery company for help, most companies can not provide a viable solution. The new network after the multi-party comparison and evaluation, choose let us finish.

[Message recovery failure analysis]

This raid problem is in fact very common, usually because the lights of the two disk is not dropped at the same time, and coincidentally, forced on-line of the early offline hard disk, resulting in the data area fresh and old mixed together, the file system structure is inconsistent. itself forced to go online, will generate a new test strip in the read and write process, so it will affect some of the data, but if read or write little or no mount at all, the severity of this disaster will be much smaller, the most serious problem in this case is rebuild TREE, Equivalent to trying to make a hybrid file system continuous. Such a result would lead to a complete error in all of the file system's structures, which is often not saved. Plus the user's file directory structure is very complex, the total number of files roughly estimated billion, but also a slim chance.

[Data Recovery Solution]

1, the file system should be tried to separate the structure of the proposed analysis, so that the workload will be much smaller, but also to provide the possibility of repeated search and analysis. However, ReiserFS file system area is relatively scattered and irregular, need to be extracted and analyzed by autonomous procedures, in this case, the light 1-level node proposed by the size of 6G, file structure is complex. (the user is also because EXT3 face such a structure collapse to choose ReiserFS, can be seen its structure complexity)

2, the file system area consistency test, equivalent to manual fsck, correcting the wrong place, in this case, a lot of file system node area because of the test relationship, so that the key attribute byte has changed. Unified initialization of all node states through the program to complete the node consistency processing

3, the completion of the above two steps after two practices, one in the Linux system again fsck, this example is not good, (because of the limited functionality of Linux fsck, the parent node is slightly wrong, its child nodes will be all into the lost+found, can not restore the original directory structure), and second, through the read-only mode, Using the Autonomic program to extract data under Windows, you need to ignore many errors, after modifying the program, use this method, all data can be extracted.

PostScript

Recently these two hard drives offline, do not know which block first away, which block after a lot of examples. It is hoped that the raid user can be treated cautiously after the two hard drives are offline, and if the logs can be traced, the logs will be OK. If the force goes wrong, you should stop the operation immediately, do not do fsck and other operations.

Warm tip: The Linux fsck risk is very large (actual Windows will also have), do try to see the hint before, if the error message is abnormal, you should choose another way. It is recommended that important data be backed up.


Enterprise mail server raid suddenly offline how to recover?

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