HP Surestore Disk Array FC60 Storage Manager 60-NT Introduction Guide - Page 45

Option, Description

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Tuning Storage Arrays Option Description 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 (writeintensive) 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. 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. 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. TUNING STORAGE ARRAYS 45

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tuning Storage Arrays
T
UNING
S
TORAGE
A
RRAYS
45
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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.
9ROXPH²*URXS²!!²&KDQJH²2ZQHUVKLS
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
.
9ROXPH²!!²&KDQJH²6HJPHQW²6L]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