Changing The Segment Size Of A Virtual Disk - Dell PowerVault MD3260i Administrator's Manual

1. In the AMW, select the Storage & Copy Services tab and select a virtual disk.
2. In the menu bar, select Storage → Virtual Disk → Change → Cache Settings.
The Change Cache Settings window is displayed.
3. Select one or more virtual disks.
To select nonadjacent virtual disks, press <Ctrl> click. To select adjacent virtual disks, press <Shift> click. To select
all of the available virtual disks, select Select All.
4. In the Cache Properties area, you can select:
– Enable read caching
– Enable write caching
* Enable write caching without batteries — to permit write caching to continue even if the RAID
controller module batteries are discharged completely, not fully charged, or are not present.
* Enable write caching with mirroring — to mirror cached data across two redundant RAID
controller modules that have the same cache size.
– Enable dynamic cache read prefetch
CAUTION: Possible loss of data—Selecting the Enable write caching without batteries option lets write
caching continue even when the batteries are discharged completely or are not fully charged. Typically, write
caching is turned off temporarily by the RAID controller module until the batteries are charged. If you select
this option and do not have a universal power supply for protection, you could lose data. In addition, you could
lose data if you do not have RAID controller module batteries and you select the Enable write caching without
batteries option.
NOTE: When the Optional RAID controller module batteries option is enabled, the Enable write caching does
not appear. The Enable write caching without batteries is still available, but it is not checked by default.
NOTE: Cache is automatically flushed after the Enable write caching check box is disabled.
5. Click OK.
A message prompts you to confirm the change in the virtual disk modification priority.
6. Click Yes.
7. Click OK.
The Change Virtual Disk Propreties - Progress dialog is displayed.

Changing The Segment Size Of A Virtual Disk

You can change the segment size on a selected virtual disk. During this operation, I/O performance is affected, but your
data remains available.
Follow these guidelines to proceed with changing the segment size:
• You cannot cancel this operation after it starts.
• Do not start this operation unless the disk group is in Optimal status.
• The MD Storage Manager determines the segment size transitions that are allowed. Segment sizes that are
inappropriate transitions from the current segment size are unavailable on the menu. Allowed transitions usually
are double or half of current segment size. For example, if the current virtual disk segment size is 32 KB, a new
virtual disk segment size of either 16 KB or 64 KB is allowed.
NOTE: The operation to change the segment size is slower than other modification operations (for example,
changing RAID levels or adding free capacity to a disk group). This slowness is the result of how the data is
reorganized and the temporary internal backup procedures that occur during the operation.
The amount of time that a change segment size operation takes depends on:
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