Virtual Disk Read Cache Policies
The read policy of a virtual disk determines how the controller handles reads to that virtual disk. The read policies are:
•Always Read
•No Read
•Adaptive Read
NOTE: The default read cache setting for virtual disks is Adaptive Read Ahead.
Reconfiguration Of Virtual Disks
An online virtual disk can be reconfigured in ways that expands its capacity and/or change its RAID level.
NOTE: Spanned virtual disks such as RAID 10, 50, and 60 cannot be reconfigured.
NOTE: Reconfiguring Virtual Disks typically impacts disk performance until the reconfiguration operation is complete.
Online Capacity Expansion (OCE) can be done in two ways:
•If there is a single virtual disk in a disk group and free space is available, the virtual disk’s capacity can be expanded within that free space.
•If a virtual disk is created and it does not use the maximum size of the disk group, free space is available.
Free space is also available when a disk group’s physical disks are replaced by larger disks using the Replace Member feature. A virtual disk's capacity can also be expanded by performing an OCE operation to add more physical disks.
RAID Level Migration (RLM) refers to changing a virtual disk’s RAID level. Both RLM and OCE can be done at the same time so that a virtual disk can simultaneously have its RAID level changed and its capacity increased. When a RLM/OCE operation is complete, a reboot is not required. See the following table for a list of RLM/OCE possibilities. The source RAID level column indicates the virtual disk RAID level before the RLM/OCE and the target RAID level column indicates the RAID level after the operation has completed.
NOTE: If the controller already contains the maximum number of virtual disks, you cannot perform a RAID level migration or capacity expansion on any virtual disk.
NOTE: The controller changes the write cache policy of all virtual disks undergoing a RLM/OCE to
Table 3. RAID Level Migration
Source RAID | Target RAID Level | Number of | Number of | Capacity | Description |
Level |
| Physical Disks | Physical Disks | Expansion |
|
|
| (Beginning) | (End) | Possible |
|
|
|
|
|
|
|
RAID 0 | RAID 0 | 1 | 2 or more | Yes | Increases |
|
|
|
|
| capacity by |
|
|
|
|
| adding disks |
RAID 0 | RAID 1 | 1 | 2 | No | Converts non- |
|
|
|
|
| redundant virtual |
18