Users Guide

• Cannot create virtual disks on PCIe SSDs.
Creating Virtual Disks Using Web interface
To create virtual disk:
1. In the iDRAC Web interface, go to Overview > Storage > Virtual Disks > Create.
The Create Virtual Disk page is displayed.
2. In the Settings section, do the following:
a) Enter the name for the virtual disk.
b) From the Controller drop-down menu, select the controller for which you want to create the virtual disk.
c) From the Layout drop-down menu, select the RAID level for the Virtual Disk.
Only those RAID levels supported by the controller appear in the drop-down menu and it is based on the RAID levels are available
based on the total number of physical disks available.
d) Select the Media Type, Stripe Size, Read Policy, Write Policy, Disk Cache Policy, T10 PI Capability.
Only those values supported by the controller appear in the drop-down menus for these properties.
e) In the Capacity field, enter the size of the virtual disk.
The maximum size is displayed and then updated as disks are selected.
f) The Span Count field is displayed based on the selected physical disks (step 3). You cannot set this value. It is automatically
calculated after selecting disks for multi-raid level. If you have selected RAID 10 and if the controller supports uneven RAID 10, then
the span count value is not displayed. The controller automatically sets the appropriate value.
3. In the Select Physical Disks section, select the number of physical disks.
For more information about the fields, see the iDRAC Online Help
4. From the Apply Operation Mode drop-down menu, select when you want to apply the settings.
5. Click Create Virtual Disk.
Based on the selected Apply Operation Mode, the settings are applied.
Creating Virtual Disks Using RACADM
Use racadm storage createvd command. For more information, see the iDRAC RACADM Command Line Reference Guide
available at dell.com/esmmanuals.
Editing Virtual Disk Cache Policies
You can change the read, write, or disk cache policy of a virtual disk.
NOTE:
Some of the controllers do not support all read or write policies. Therefore, when a policy is applied, an error
message is displayed.
The read policies indicate whether the controller must read sequential sectors of the virtual disk searching for data:
• Adaptive Read Ahead — The controller initiates read ahead only if the two most recent read requests accessed sequential sectors
of the disk. If subsequent read requests access random sectors of the disk, the controller reverts to no read ahead policy. The
controller continues to evaluate whether read requests are accessing sequential sectors of the disk, and initiates read ahead if
necessary.
• Read Ahead — The controller reads sequential sectors of the virtual disk when seeking data. Read ahead policy may improve system
performance if the data is written to the sequential sectors of the virtual disk.
• No Read Ahead — Selecting no read ahead policy indicates that the controller should not use read ahead policy.
The write policies specify if the controller sends a write-request completion signal as soon as the data is in the cache or after it has been
written to the disk.
• Write Through — The controller sends a write-request completion signal only after the data is written to the disk. Write-through
caching provides better data security than write-back caching, since the system assumes the data is available only after it has been
safely written to the disk.
• Write Back — The controller sends a write-request completion signal as soon as the data is in the controller cache but has not yet
been written to disk. Write back caching may provide improved performance since subsequent read requests can retrieve data quickly
from the cache then from the disk. However, data loss may occur in the event of a system failure which prevents that data from being
written on a disk. Other applications may also experience problems when actions assume that the data is available on the disk.
• Force Write Back — 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.
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Managing Storage Devices