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 inaccessible. 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.
To ensure a successful data
recovery, it is important that the failed RAID 5 remain intact.
More information can be found by visiting our
RAID 5 recovery page.
