– 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 interfaceTo 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 areavailable 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 automaticallycalculated after selecting disks for multi-raid level. If you have selected RAID 10 and if the controller supports uneven RAID10, 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 Help4. 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 RACADMUse the racadm storage createvd command.For more information, see the iDRAC RACADM Command Line Reference Guide available at dell.com/idracmanuals.Editing virtual disk cache policiesYou 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 errormessage 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 sequentialsectors of the disk. If subsequent read requests access random sectors of the disk, the controller reverts to no read aheadpolicy. The controller continues to evaluate whether read requests are accessing sequential sectors of the disk, and initiates readahead if necessary.NOTE: Previous generations of PERC controllers support read policy settings of No Read Ahead, Read Ahead, andAdaptive Read Ahead. With PERC 8 and PERC 9, the Read Ahead and Adaptive Read Ahead settings are functionallyequivalent at the controller level. For backward compatibility purposes, some systems management interfaces andPERC 8 and 9 controllers still allow setting the read policy to Adaptive Read Ahead. While it is possible to set ReadAhead or Adaptive Read Ahead on PERC 8 or PERC 9, there is no functional difference.• Read Ahead — The controller reads sequential sectors of the virtual disk when seeking data. Read ahead policy may improvesystem 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.199
