There are basically two types of RAID data recovery. First, and normally the most difficult, is a recovery of the RAID itself. Whether it is a RAID 5, RAID Zero, or JBOD, faulty drives, corrupted firmware, failed controller, or power surges can cause a RAID to degrade and go offline. This type of recovery requires a skilled technician who is well versed in RAID theory and technology and also has a clear understanding of file system architecture and the anomalies created when a RAID has failed. Specifically this involves the possibility of a stale drive in a RAID Five, the offset points in an LVM JBOD RAID, or data corruption due to synchronization issues in a RAID One. This type of recovery is much more costly than it is to recover deleted files on raid and can ultimately cost thousands of dollars to the client.
The second type of recovery is a RAID that involves data that has been deleted. The assumption is made that the RAID is currently in working order and mounted so that tools used for standard deleted files on non-RAID systems can be used. From a standalone RAID on an end users system to a high end enterprise NAS device with fiber channel and an iSCSI interface to recover deleted files on RAID is for all practical purposes the same.
In order to recover deleted files on RAID device you must take several things into consideration that are not part of the standard recovery.
First of all, many RAID systems are file servers and as such, have several users accessing it through the network. Many times a user will not only save data on the server but will also save it locally. End users will at times use the file server as an archive for finished products but their work product is stored locally. Before bringing software solutions to recover deleted data check the user’s local storage and see if in fact the data is there.
Since the majority of RAID systems are file servers a deleted file is much more vulnerable to the possibility of being over written. If a file has been deleted from an active server for more than twenty-four hours then it is more than likely that it has been over written and is therefore corrupted. Depending upon the file type the corruption may be irreversible.
Many RAID systems are used as a database back end’s and house large files such as files for MySQL, SQLServer, QuickBooks, and many others. If any of the primary flat files for these types of applications are deleted the possibility of restoring the deleted file becomes virtually nonexistent.
As a rule of thumb, recovery of deleted files on a RAID server depend upon two crucial points. Is it a RAID server, and is the server active. Although there are many other issues that affect a full restoration of a deleted file these two points are the most salient.