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Appendix C RAID
16
(3) RAID5
This method slices data (sent from the host) in certain striping size and distributes the data to the
physical disks of the RAID. It also distributes the parity data to the disks.
Since RAID5 distributes parity data to multiple disks, it enables concurrent processing at disk
access. Thus, RAID5 is suitable for processing which often makes random access to small files
in size of several kilobytes.
Even if one of the disks fails, access can be made to the parity data. However, performance in
read operation lowers in this case.
<Advantage>
y Concurrent processing by using distributed parity data
y Availability of processing which often makes random access
<Disadvantage>
y If one of the physical disks constituting logical disks fails, performance in read operation
lowers.
Data Sent from Host
S
t
r
ip
e
1
S
t
r
ip
e
2
S
t
r
ip
e
3
S
t
r
ip
e
4
S
t
r
ip
e
N
Stripe1
Stri
p
e4
Stri
p
e2
Stri
p
eN
Stri
p
e3
Physical Disk1 2 3
Striping Size
Parity(1,2)
Parity(3,4)
Parity(N,N+1)
StripeN+1
Parity Generation