RAID5 have a hard drive offline, do not recommend to do rebuild immediately

[Data Recovery issues]

RAID5 when a hard drive offline, processing degraded state, this time the normal suggestion is to replace the hard disk to do rebuild to restore the complete data status, if there is hot spares, will automatically do rebuild, this is appropriate?

Answer

A set of RAID volumes will rarely read all of the disk space on the physical hard disk after a long period of time, which is even more impossible. In some cases, the hard drive will produce bad results in areas that are not read, or where the previous read is good, which is good for the controller because it is not read or written. The most immediate hazard to producing this bad track is in the rebuild process. When a physical hard drive is offline, usually all the technical staff and official information will be written as soon as possible, but if the other hard disk exists in this kind of usual rebuild bad track, rebuild and all do full synchronization, will certainly read and write to those bad way, this time rebuild unfinished, new disk can not be online , because of the bad track found in the old disk, it will lead to raid and some of the offline hard drive, which may cause raid failure, unable to recover the data itself.

Therefore, when a raid is processing a degraded state, such as a small amount of important data, it is recommended that the backup be done first, and of course this should be a different machine and not be backed up to the currently degraded raid.

If there is another hard drive offline in rebuild causing the RAID volume offline, must not rebuild raid, such as determined after the offline hard drive, can be forced online recovery data (some controllers do not have options, there is no way to do), can also be consulted data recovery company for processing.

North Asia Data Recovery Center, http://www.datahf.net