HP Smart Array Controller technology, 4th edition

6
take corrective actions, provide automatic recovery, and deliver full fault management to protect against
downtime.
Adjusting strip size with the Array Configuration Utility (ACU)
You can change the strip size of a logical drive, a process called strip-size migration, without any downtime
by using the Array Configuration Utility, a browser-based graphical application that helps configure Smart
Array controllers.
You can use strip size migration to improve logical drive performance if your read/write environment
changes. All RAID levels supported have a default strip-size of 256 KiB. The default provides good
performance across many types of applications. You can set the strip-size to 8, 16, 32, 64, 128, or 256
KiB for all supported RAID levels. You can also set the strip-size to 512 KiB for RAID 50. These values can
change for certain controllers and storage device implementations. You should consult configuration
documentation for your specific controller and storage device.
Certain applications, especially those performing mostly one type of transaction, write transactions for
example, may require you to adjust the strip-size to achieve optimal performance. Table 1 lists
recommended strip sizes for general types of server applications. You can start with these general
recommendations and then fine-tune to determine the best overall performance for a particular application.
The ACU lets you make these changes online without disruption or data loss. For more about the ACU, see
the “Storage management
” section later in this paper.
Table 1. Recommended strip sizes
Type of server application Suggested strip size
Mixed read/write Default value
Mainly sequential read (such as audio/video
applications)
Larger strip sizes
Mainly write (such as image manipulation
applications)
Smaller strips for RAID 5, RAID 6
Larger strips for RAID 0, RAID 1, RAID 1+0
RAID migration with ACU
Using the ACU, you can also change the RAID level of the logical drive without downtime, maintaining
data availability. You can increase raw data storage capacity, increase the number of spindles in a logical
drive, or change fault tolerance (RAID) configurations with a RAID migration.
Drive roaming
Drive roaming lets you move disk drives and arrays while maintaining data availability. You can move one
or more disk drives in a configured logical drive to a different bay position as long as the new bay position
is accessible by the same controller. In addition, you can move a complete array from one controller to
another, even if controllers are in different servers.
Drive roaming is an offline feature. There is no method for removing an array while the server is online and
then moving it to a new physical location.
Mirror splitting and recombining with the ACU
You can use the ACU to split an array with one or more RAID 1 or RAID 1+0 logical drives into two
identical new RAID 0 arrays. This is useful if you want to replicate a configuration or need to build a
backup before performing a risky operation.