Dell PowerEdge RAID Controller 9 User’s Guide H330, H730, and H830

Setting up virtual disks

You can set up a disk group and create virtual disks using the procedures in this section. Each procedure is explained individually in this section in detail.

1. Create virtual disks. See Creating virtual disks.
2. Select the virtual disk options.
3. Designate hot spares (optional).
   For more information, see Managing dedicated hot spares.
4. Initialize the virtual disks.
   NOTE:When you use one physical disk group to create multiple virtual disks, all the virtual disks must be configured with the same RAID level.

   When you define the virtual disks, you can set the following virtual disk parameters:

   • RAID level
   • Stripe element size
   • Read policy
   • Write policy
   • Type of initialization
   • Hot spare configuration
     NOTE:The default hard drive cache policy for a virtual disk with SAS hard drives is disabled, and the cache policy for a virtual disk with SATA hard drives is enabled. The Virtual Disk parameter cannot be changed in the BIOS Configuration Utility Ctrl R . Use Dell OpenManage Storage Management for the hard drive cache setting operation.

     The following table shows the parameters that you can configure when defining virtual disks.

   Table 1. Parameters — descriptionParameters — description

   Parameter	Description
   RAID Level	Specifies whether the virtual disk is RAID 0, 1, 5, 6, 10, 50, or 60. The number of disks, disk capacity, requirements for fault tolerance, performance, and capacity should be considered when selecting the RAID level.
   Stripe Element Size	Specifies the size of the segments written to each physical disk in a RAID 0, 1, 5, 6, 10, 50, and 60 virtual disk. You can set the stripe element size to 64 KB 128 KB, 256 KB, 512 KB, or 1 MB. The default and recommended stripe element size is 64 KB. A larger stripe element size provides better read performance if your system mostly does sequential reads.
   Write Policy	Specifies the controller write policy. You can set the write policy to Write-Back or Write-Through. In Write-Back caching, the controller sends a data transfer completion signal to the host when the controller cache has received all the data in a transaction. NOTE:If a Battery Backup Unit (BBU) is present, the default cache setting is Write-Back. If no BBU is present, the default cache policy default setting is Write-Through. NOTE:If Write-Back is enabled and the system is turned off and then on, the controller may pause as the system flushes cache memory. Controllers have a battery backup default to Write-Back caching. In Write-Through caching, the controller sends a data transfer completion signal to the host when the disk subsystem has received all the data in a transaction.
   Read Policy	Read-Ahead enables the read-ahead feature for the virtual disk. You can set the parameter to Read-Ahead or No-Read-Ahead. The default is Read-Ahead. Read-Ahead specifies that the controller uses Read-Ahead for the current virtual disk. Read-Ahead capability allows the controller to read sequentially ahead of requested data and store the additional data in the cache memory, anticipating that the data is required soon. No-Read-Ahead specifies that the controller does not use read ahead for the current virtual disk.