Users Guide

● There are limitations on the number of physical disks that can be included in the virtual disk. These limitations depend on the
controller. When creating a virtual disk, controllers support a certain number of stripes and spans (methods for combining
the storage on physical disks). Because the number of total stripes and spans is limited, the number of physical disks that
can be used is also limited. The limitations on stripes and spans affect the RAID levels as follows:
○ Maximum number of spans affects RAID 10, RAID 50, and RAID 60.
○ Maximum number of stripes affects RAID 0, RAID 5, RAID 50, RAID 6, and RAID 60.
○ Number of physical disks in a mirror is always 2. This affects RAID 1 and RAID 10.
● 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 Storage > Overview > Virtual DisksAdvanced Filter.
2. In the Virtual Disk section, do the following:
a. From the Controller drop-down menu, select the controller for which you want to create the virtual disk.
b. 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.
c. Select the Media Type, Stripe Size, Read Policy, Write Policy, Disk Cache Policy, .
Only those values supported by the controller appear in the drop-down menus for these properties.
d. In the Capacity field, enter the size of the virtual disk.
The maximum size is displayed and then updated as disks are selected.
e. 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.
NOTE:
You can use alphanumeric characters, spaces, dashes, and underscores in the disk name. Any other special
characters that you enter are removed while creating the virtual disk.
Creating virtual disks using RACADM
Use the racadm storage createvd command.
For more information, see the iDRAC RACADM CLI Guide available at www.dell.com/idracmanuals.
NOTE: Disk slicing or configuring partial VDs is not supported using RACADM on the drives managed by S140 controller.
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 reads 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.
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Managing storage devices