We provide extensive RAID recovery services. The safe and proper way is to image all the drives of the RAID array first, then work on those images to rebuilt the data. We often need to repair one or more drive from electronic or mechanical failure first then image afterwards.
In theory, we should not have to perform raid 5 data recovery, since this type of RAID can work in degraded mode until your replace the bad drive, then everything is back to normal once the RAID 5 rebuilt itself.
The most common mistake and RAID 5 is when a good disk is replaced instead of the bad one. An immediate failure occurs since most RAID can’t work with 2 disks basically not working. The same problem occurs if the user specify a wrong number of disk while rebulding the failed RAID. This happens often due to the use of a hot spare which is not in theory part of the raid itself.
On the opposite, RAID 0 recovery is common, since this type of RAID offers not tolerance to failure. If any of the drive crash or fail, then your data are gone. We perform a lot of raid recovery on RAID 0.
There is one case, where we can’t recover any data though. If a RAID is reinitiliazed (which takes hours), all data will be lost. It will basically write 0 over the entire disks. There will be no data left to be recovered.