HP StorageWorks 500 Modular Smart Array - Manual (Page 76)

Configuration and Utilities
HP StorageWorks Modular Smart Array 500 System User Guide 4-13
Priority Settings
To set the drive rebuild priority:
1. Highlight the MSA500 controller.
2. Select the controller settings.
— If you choose low priority for drive rebuild, drive rebuilding takes place
when I/O to the drive is inactive.
— If you choose high priority, drive rebuilding occurs faster, at the expense of
normal I/O operations.
Accelerator Ratio
The MSA500 controller has an onboard cache called an Array Accelerator, which
performs both write-posting and read-ahead caching. The setting in CPQONLIN
determines the amount of memory allocated to the read and write caches. For
example, if the Accelerator Ratio is set to Read 75%:Write 25%, 75% of Array
Accelerator cache is dedicated to read-ahead cache and 25% is dedicated to the write-
posting cache. This option can be modified from the controller Settings menu.
Expanding an Array
During an expand, performance may be slightly degraded. In most cases, however,
any potential degradation is offset by the addition of physical drives. Some tips for
expanding include:
• Perform the expand process during periods of low server use. If you must expand
during peak periods, ACU for NetWare enables you to set the priority of the
expand. Setting the priority to LOW affects performance the least, but it takes
longer for the new space to become available.
• When expanding, always add drives with a capacity equal to or greater than the
capacity of the smallest drive in the array. Adding larger drives wastes space
because only the space that is equal to the smallest drive size can be used.