Administrator Guide

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 Properties - Progress dialog is displayed.
Changing segment size of 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:
• The I/O load from the host
• The modification priority of the virtual disk
• The number of physical disks in the disk group
• The number of physical disk ports
• The processing power of the storage array RAID controller modules
If you want this operation to complete faster, you can change the modification priority to the highest level, although this may decrease
system I/O performance.
To change the segment size of a virtual disk:
1. In the AMW, select the Storage & Copy Services tab and select a virtual disk.
2. From the menu bar, select Storage > Virtual Disk > Change > Segment Size.
3. Select the required segment size.
A message prompts you to confirm the selected segment size.
4. Click Yes.
The segment size modification operation begins. The virtual disk icon in the Details pane shows an Operation in Progress status while
the operation is taking place.
NOTE:
To view the progress or change the priority of the modification operation, select a virtual disk in the disk
group, and from the menu bar, select Storage > Virtual Disk > Change > Modification Priority.
Changing the I/O type
You can specify the virtual disk I/O characteristics for the virtual disks that you are defining as part of the storage array configuration. The
expected I/O characteristics of the virtual disk is used by the system to indicate an applicable default virtual disk segment size and
dynamic cache read prefetch setting. .
NOTE:
The dynamic cache read prefetch setting can be changed later by selecting Storage > Virtual Disk > Change >
Cache Settings from the menu bar. You can change the segment size later by selecting Storage > Virtual Disk > Change
> Segment Size from the menu bar.
Disk groups, standard virtual disks, and thin virtual disks 61