Users Guide

The Disk Cache policy apply to readings on a specific virtual disk. These settings do not affect the read-ahead policy.
NOTE:
• Controller non-volatile cache and battery backup of controller cache affects the read-policy or the write policy that a
controller can support. All PERCs do not have battery and cache.
• Read ahead and write back requires cache. Therefore, if the controller does not have cache, it does not allow you to
set the policy value.
Similarly, if the PERC has cache but not battery and the policy is set that requires accessing cache, then data loss
may occur if base of power off. So few PERCs may not allow that policy.
Therefore, depending upon the PERC, the policy value is set.
Deleting Virtual Disks
Deleting a virtual disk destroys all information including file systems and volumes residing on the virtual disk and removes the virtual disk
from the controller’s configuration. When deleting virtual disks, all assigned global hot spares may be automatically unassigned when the
last virtual disk associated with the controller is deleted. When deleting the last virtual disk of a disk group, all assigned dedicated hot
spares automatically become global hot spares.
You must have the Login and Server Control privilege to perform delete virtual disks.
When this operation is allowed, you can delete a boot virtual drive. It is done from sideband and the independent of the operating system.
Hence, a warning message appears before you delete the virtual drive.
If you delete a virtual disk and immediately create a new virtual disk with all the same characteristics as the one that was deleted, the
controller recognizes the data as if the first virtual disk were never deleted. In this situation, if you do not want the old data after
recreating a new virtual disk, re-initialize the virtual disk.
Checking Virtual Disk Consistency
This operation verifies the accuracy of the redundant (parity) information. This task only applies to redundant virtual disks. When
necessary, the check consistency task rebuilds the redundant data. If the virtual drive has a degraded status, running a check consistency
may be able to return the virtual drive to ready status. You can also cancel the check consistency operation.
The cancel check consistency is a real-time operation.
You must have Login and Server Control privilege to check consistency of virtual disks.
Initializing Virtual Disks
Initializing virtual disks erases the all the data on the disk but does not change the virtual disk configuration. You must initialize a virtual disk
that is configured before it is used.
NOTE:
Do not initialize virtual disks when attempting to recreate an existing configuration.
You can perform a fast initialization, a full Initialization, or cancel the initialization operation.
NOTE:
The cancel initialization is a real-time operation. You can cancel the initialization using only the iDRAC Web
interface and not RACADM.
Fast Initialization
The fast initialize operation initializes all physical disks included in the virtual disk. It updates the metadata on the physical disks so that all
disk space is available for future write operations. The initialize task can be completed quickly because the existing information on the
physical disks is not erased, although future write operations overwrite any information that remains on the physical disks.
Fast initialization only deletes the boot sector and stripe information. Perform a fast initialize only if you are constrained for time or the
hard drives are new or unused. Fast Initialization takes less time to complete (usually 30-60 seconds).
CAUTION:
Performing a fast initialize causes existing data to be inaccessible.
The fast initialize task does not write zeroes to the disk blocks on the physical disks. It is because the Fast Initialize task does not perform
a write operation, it causes less degradation to the disk.
Managing Storage Devices
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