Storage Manager 60-NT Introduction Guide
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tuning Storage Arrays
T
UNING STORAGE ARRAYS 45
9ROXPH*URXS!!&KDQJH5$,'/HYHO Use this option to change the RAID level of a volume group
when either:
The application read or write percentages on a volume indicate
that its current RAID level may not be appropriate for desired
performance
-or-
You want to change the volume group’s redundancy (such as
changing from RAID 0 to RAID 5)
Applications with a high read percentage will do very well using
RAID level 5 volumes because of the outstanding read
performance of the RAID level 5 configuration.
However, applications with a low read percentage (write-
intensive) do not perform as well on RAID 5 volumes because of
the way a controller writes data and redundancy data to the
drives in a RAID 5 volume group. If there is a low percentage of
read activity relative to write activity, you might consider
changing the RAID level of a volume group from RAID 5 to RAID
1 for faster performance.
9ROXPH*URXS!!&KDQJH2ZQHUVKLS If a particular controller has considerably more I/O activity than
expected, consider moving a volume group to the other
controller in the Storage Array using the
Volume Group >> Change Ownership option.
9ROXPH!!&KDQJH6HJPHQW6L]H A segment is the amount of data in Kilobytes (KB) that the
controller writes on a single drive in a volume before writing data
on the next drive.
When you create a volume, the default segment size is normally
a good choice for the expected volume usage you specify. If
volume usage is different than expected, use this option to
change the segment size of a volume.
In a read-intensive application environment with random I/O
access patterns, make sure the segment size is large enough to
minimize the number of drives needed to satisfy an I/O request.
This leaves other drives available to satisfy other requests.
In a single user environment with sequential I/O access
patterns, performance is optimized when a single I/O request
can be serviced with a single volume group data stripe (the
segment size multiplied by the number of drives in the volume
group used for I/O). In this case, multiple disks are used for the
same request, but each disk is only accessed once.
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Option Description