How Data Recovery is Performed on Failed RAID 5 Arrays

RAID 5 arrays are used for many applications because they are for the most part cost-effective and provide a level of fault tolerance not provided by some other levels of RAID. As with any RAID level, RAID 5 can experience many different types of problems. This article will provide a brief discussion of some of the problems causing RAID 5 failure and how data recovery can work to solve these problems.

Problems That Can Cause RAID 5 Failure

Bad Sectors

A RAID 5 can fail due to bad sectors on any of the disks in the array. This can force the array to go offline.

Corrupt Data

A RAID 5 can suffer from corrupt data due to many reasons including viruses, user error, overwriting files, and scratches on the surface of the disk platters.

Degraded RAID 5

A RAID 5 becomes degraded when there is a loss of one of the member disks. This causes a huge decrease in performance and also removes the fault tolerance of the RAID 5. Operating a degraded RAID 5 is dangerous because the loss of a second disk will cause the entire array to be lost.

Deleted Files

Many times a user will accidentally delete important data in a RAID 5 array. Other times, it is done intentionally by disgruntled employees. In most situations, deleted files can be recovered.

Missing Partitions

In many cases, the partition table can become corrupt or missing causing an entire partition to disappear or become unusable. This makes data recovery necessary. Attempting recovery with software will increase the risk of permanent data loss.

RAID 5 Controller Failure

A Hardware RAID 5 array uses a controller which contains all of the logic and handles the operations of the array. For many reasons, the array can experience a controller failure. This can cause the array to not boot. It could also cause the logical volume to disappear.

RAID 5 Disk Failure/RAID 5 Drive Failure

A RAID 5 is a set of three or more disk drives. Any of these drives can experience failure. A RAID 5 is configured with the ability to withstand the failure of only one disk at a time. In most cases, the RAID can be recovered in a data recovery lab using parity data written to the disks by the array. Even if more than one disk has failed, data recovery is still possible in a recovery lab.

RAID 5 Firmware Failure

Firmware problems can occur in the RAID controller or the member disk drives.

RAID 5 Rebuild Failure

For various reasons, a RAID 5 array can experience a rebuild failure. This may keep member disks offline and render the array unusable.

Server Crash

Many times, the host server experiences problems and can crash. This of course makes the array unaccessible. A data recovery lab can recover the data from the member disks.

How to Ensure RAID 5 Data Recovery is Successful

If you have experienced a RAID 5 failure, it is important that you do not take matters into your own hands. This can cause the parity data to be overwritten. Parity data, which is written to the member disks, is in many cases vital to ensure a successful recovery. The very first thing you should do is power off the RAID server immediately to ensure that no additional writes are performed. Any events describing what may have happened to cause the problem should be noted. If the member disk drives are removed from the server, they should be labeled in the correct order they were removed. The disk order is very important if time is of the essence. This is also important if you have a large number of member disks.