Users Guide

● OCE/RLM is restricted to the scenario where the disk group contains only one VD.
● OCE is not supported on RAID50 and RAID60. RLM is not supported on RAID10,RAID50 and RAID60.
● 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.
● The controller changes the write cache policy of all virtual disks undergoing a RLM/OCE to Write-Through until RLM/OCE is
complete.
● Reconfiguring Virtual Disks typically impacts disk performance until the reconfiguration operation is complete.
● The total number of physical disks in a disk group cannot exceed 32.
● If any background operation (like BGI/rebuild/copyback/patrol read ) is already running on the corresponding VD/PD then
Reconfiguration (OCE/RLM) is not allowed at that time.
● Any kind of disk migration when Reconfiguration (OCE/RLM) is on progress on drives associated with VD causes
reconfiguration to fail.
● Any new drive added for OCE/RLM becomes part of the VD after reconstruction completes. But State for those new drive
changes to Online just after reconstruction starts.
Cancel Initialization
This feature is the ability to cancel the background initialization on a virtual disk. On PERC controllers, the background
initialization of redundant virtual disk starts automatically after a virtual disk is created. The background initialization of
redundant virtual disk prepares the virtual disk for parity information and improves write performance. However, some
processes such as creating a virtual disk cannot be run while the background initialization is in progress. Cancel Initialization
provides the ability to cancel the background initialization manually. Once cancelled, the background initialization automatically
restarts within 0 to 5 minutes.
NOTE: Background initialization is not applicable for RAID 0 virtual disks.
Managing virtual disks using web interface
1. In the iDRAC web interface, go to Configuration > Storage Configuration > Virtual Disk Configuration.
2. From the Virtual Disks, select the controller for which you want to manage the virtual disks.
3. From Action drop-down menu, select an action.
When you select an action, an additional Action window displayed. Select / enter the desired value.
● Rename
● Delete
● Edit Cache Policy — You can change the cache policy for the following options:
○ Read Policy — Following values are available for selection:
￭ Adaptive Read Ahead — Indicates that for the given volume, the control uses the Read-Ahead cache policy if
the two most recent disks accesses occurred in sequential sectors. If the read requests are random, the controller
returns to No Read Ahead mode.
￭ No Read Ahead — Indicates that for the given volume, no read ahead policy is used.
￭ Read Ahead — Indicates that for the given volume, the controller reads sequentially ahead of the requested data
and stores the additional data in cache memory, anticipating a data requirement. This speeds up sequential data
reads, but there is less improvement when accessing random data.
○ Write Policy — Change the write cache policy to one of the following options:
￭ Write Through — Indicates that for the given volume, the controller sends a data transfer completion signal to
the host system when the disk subsystem has received all the data in a transaction.
￭ Write Back — Indicates that for the given volume, the controller sends a data transfer completion signal to the
host system when the controller cache has received all the data in a transaction. The controller then writes the
cached data to the storage device in the background.
￭ Force Write Back — When using force write-back caching, the write cache is enabled regardless of whether the
controller has a battery. If the controller does not have a battery and force write-back caching is used, data loss
may occur in the event of a power failure.
○ Disk Cache Policy — Change the disk cache policy to one of the following options:
￭ Default — Indicates that the disk is using its default write cache mode. For SATA disks, this is enabled and for
SAS disks this is disabled.
￭ Enabled — Indicates that the disk’s write cache is enabled. This increases performance and the probability of
data loss if there is power loss.
Managing storage devices
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