With no dedicated
parity drive the write performance is better,
with overlapped data and parity update writes.
Read operations can be interleaved as all drives
contain data stripes. RAID 1 performs faster but
RAID 5 provides better storage efficiency. Parity
update can be more efficiently handled by RAID
5, by checking for data bit changes and only changing
the corresponding parity bits. For small data
writes improvements here are lost as most disk
drives update sectors entirely for any write operation.
For larger writes only the sectors where bit changes
need to be made are rewritten and improvements
made. Maintaining parity information reduces write
performance ? in some cases as low as one third
the speed of RAID 1. For this reason RAID 5 is
not normally used in performance critical processes.
RAID 5 provides
fair data security and needs three or more disk.
If one of the hard fails, the Raid can let the
user access the data and will be working but at
degraded level. Some Raids will use the hot spare
drive by themselves and rebuild the RAID. A hot-spare
drive is a hard disk drive in a server that is
defined for automatic use in the event of a drive
failure. If a drive fails, the system can automatically
switch to the hot-spare drive, and the data from
the dead drive is reconstructed on the hot-spare
drive. The system does not need to be shut down
and the controller card will do the rebuilding.
In others, user have to shut down the RAID to
replace the faulty drive. At degraded level, there
is no fault tolerance. User must replace the faulty
drive as soon as possible to lesson the chances
of data loss. If any of the drives in the degraded
RAID had a problem, the data loss is inevitable.
In RAID-5, data
is lost when user have problem with more than
one disk drives. If you have problem with the
RAID 5, check the drives and make sure if they
working physically. In most systems, the green
light on hard drive containers will let you know,
if it is working. You can also see the drive in
If two or more drives
have problems, shut down the server. You need
professional help. Further working with the RAID
may lead to complete loss of data.
Please don't regenerate
or rebuild the RAID, if two or more drives have
physical problem. This can lead to complete data
loss. If you had a problem, give us call for further
assistance for RAID 5 data recovery.