Many of the raid 5 systems, like QNAP, that DTI Data Recovery sees are ones that have seen multiple drive failures but without drive replacement and rebuild. This type of RAID 5 data recovery lends itself to the technician finding a stale drive and eliminating it from the recovery set. In some files systems it is very easy to look at each disk and determine which drive is in fact stale. There are methods and software that allows the technician to use embedded information in the file system to determine which drive is stale and which drives were active during the service of the array.
With that being said, there are times when multiple disks fail in the array in close proximity. Many of these raid 5 arrays will have failures during the rebuild of a drive and the other drives will fail due to stress placed on the array. This is due many times to the fact that a rebuild is one of the most taxing functions that can be placed on a raid system and should be monitored using extreme caution.
In order to avoid most anomalies when reconstructing an array the following checklist should be performed.
Scan all disks for errors
DTI data offers software on our website at no charge that will allow a technician to scan the surface of each drive in the array. The scanning of a drive will alleviate the vast majority of RAID 5 data recovery problems that may come up during a rebuild.
Check each disks PoH (Power on Hours)
There has been many times where looking at the power on hours of a disk gave a real indication of which drive is the stale drive. It is a simple matter of finding which disk has the shortest PoH and using that as one determining factor in eliminating a stale drive. There are several public domain software that will give a technician that information.
Clone drives with bad sectors
In order to help ensure no failures during a raid rebuild make sure that all drives have no read errors. This is the single most prevalent cause of a raid rebuild failure. After you have scanned the drive in the first step, check the error report for any bad sectors and if some are found use DTI Data’s cloning software, Speed Clone, to clone the data onto a new drive using that drive for the rebuild.
These suggestions are just a few of the many things that should be done in order to ensure a safe rebuild.