Accusys ExaRAID GUI - Manual (Page 95)

Using the RAID GUI
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2.7.15 Cache Configurations
In this section, you can configure the following settings to the controller.
The settings of Cache Unit Size, Auto Array Roaming Control, and Write
Log Control will take effect after you restart the RAID subsystem.
2.7.16 Miscellaneous
Cache Unit Size (KB): 4 / 8/ 16 / 32 / 64 / 128 (default)
The cache unit size must be smaller or equal to the minimum stripe
size of existing logical disks.
Read Ahead Expire Control (1/100 second):55 (default)
Specify the read ahead expire control in 1/100 seconds.The range is
from 10 to 1000.
Write Cache Periodic Flush (second): 5 (default)
Specify the period in seconds to periodically flush the write cache. If
0 is specified, periodic cache flushing is disabled. The range is from 0
to 999.
Write Cache Flush Ratio (%): 45 (default)
Specify the dirty write buffer watermark. When the specified
percentage is reached, the system will start to flush the write buffers
immediately. The range is from 1% to 100%.
Mirrored Write Cache Control: On (default) / Off
This option is only available on the redundant-controller system. If this
option is enabled, all written data from hosts will be mirrored to the
peer controller.
Note
Disable Mirrored Write Cache Control function will improve the write
performance, but it will cause data loss when a controller fails. Do
not disable it if you set active-active redundant controller
configuration.
Auto Spare Control: On (default) / Off
If this option is enabled, and there is no global spare disk, unused
hard disks are used for rebuilding. If there are multiple unused disks,
the disk with the lowest hard disk identifier will be used.
Spare Restore Control: On / Off (default)
If this option is enabled, the controller will restore the data from the
spare disk to a new replacement disk when inserted. This allows the
user to keep the same member disks as original.