IBM System Storage DS3500 Introduction And Implementation Manual page 80

7914DS3KPlanning_090710.fm
It has additional costs because of the extra disk capacity required by using two parity
blocks per stripe: compared to a RAID 5 array, additional drives are required to achieve
that same usable logical drive capacity.
Any application that has high read request rates and average write request rates such as
Transaction servers, Web servers, data mining applications, and Exchange servers will
benefit from RAID 6.
RAID Levels summary
In this section we summarize the general characteristics of the various RAID levels supported
by the DS3500 storage subsystem. The following note and Table 3-3 summarize this
information.
Summary: The general performance characteristics of the various RAID levels are:
RAID 0 offers high performance, but does not provide any data redundancy.
RAID 1/10 offers high performance for write-intensive applications.
RAID 3 is good for large data transfers in applications, such as multimedia or medical
imaging, that write and read large sequential chunks of data.
RAID 5 is good for multi-user environments, such as database or file system storage,
where the typical I/O size is small, and there is a high proportion of read activity.
RAID 6 offers high availability with performance slightly lower than RAID 5.
Table 3-3 RAID levels comparison
RAID
0
1/10
3
5
56
IBM System Storage DS3500: Introduction and Implementation Guide
Description Application
Stripes data across IOPS
multiple drives. Mbps
The drive data is IOPS
mirrored to another
drive.
Drives operate Mbps
independently with
data blocks
distributed among all
drives. Parity is
written to a dedicated
drive.
Drives operate IOPS
independently with Mbps
data and parity blocks
distributed across all
drives in the group.
Draft Document for Review March 28, 2011 12:24 pm
Advantage
Performance, due to
parallel operation of the
access.
Performance, as
multiple requests can
be fulfilled
simultaneously.
High performance for
large, sequentially
accessed files (image,
video, and graphics).
Good for reads, small
IOPS, many concurrent
IOPS, and random I/Os.
Disadvantage
No redundancy. If one
drive fails, the data is
lost.
Storage costs are
doubled.
Degraded
performance with 8-9
I/O threads, random
IOPS, and smaller,
more numerous
IOPS.
Writes are particularly
demanding.