Specifying the Virtual Drive Parameters

> Specifying the Virtual Drive Parameters

> This section explains the virtual drive options that are set using the manual procedures for creating RAID drive groups for RAID levels RAID 0, RAID 00, RAID 1, RAID 5, RAID 6, RAID 10, RAID 50, and RAID 60.

> | RAID Level: The drop-down list shows the possible RAID levels for the virtual drive.

> | RAID 0: Select this option for RAID 0.

> | RAID 00: Select this option for RAID 00.

> | RAID 1: Select this option for RAID 1.

> | RAID 5: Select this option for RAID 5.

> | RAID 6: Select this option for RAID 6.

> | RAID 10: Select this option for RAID 10.

> | RAID 50: Select this option for RAID 50.

> | RAID 60: Select this option for RAID 60.

> You can select the VD settings when you use the advanced configuration procedure to create virtual drives. You must change these parameters only if you have a specific reason for doing so. It is usually best to leave them at their default settings.

> | Virtual drive name: Provide a name for the VD.

> | Capacity: Enter the capacity of the VDs in the drive group.

> | Initialization state: Initialization prepares the storage medium for use. Specify the initialization status:

> | No Initialization: (the default) The new configuration is not initialized, and the existing data on the drives is not overwritten.

> | Fast Initialization: Firmware quickly writes 0s to the first and last 8-MB regions of the new virtual drive and then completes the initialization in the background. This lets you start writing data to the virtual drive immediately.

> | Full Initialization: A complete initialization is done on the new configuration. You cannot write data to the new virtual drive until the initialization is complete. This process can take a long time if the drives are large.

> NOTE BGI is supported only for RAID 5 and RAID 6 and not for any other RAID levels. RAID 5 virtual drives require at least five drives for a background initialization to start. RAID 6 virtual drives require at least seven drives for a background initialization to start. If there are fewer drives, the background initialization does not start.

> | Strip size: The strip size is the portion of a stripe that resides on a single drive in the drive group. The stripe consists of the data segments that the controller writes across multiple drives, not including parity drives. For example, consider a stripe that contains 64 KB of drive space and has 16 KB of data residing on each drive in the stripe. In this case, the stripe size is 64 KB, and the strip size is 16 KB. Strip sizes of 8 KB, 16 KB, 32 KB, 64 KB, 128 KB, 256 KB, 512 KB, and 1024 KB are supported. The default is 64 KB.

> NOTE You cannot select 8 KB as the strip size when you create a RAID 6 drive group with three drives or a RAID 60 drive group with six drives.

> | Read policy: Specify the read policy for this virtual drive:

> | Always read ahead: Read ahead capability allows the controller to read sequentially ahead of requested data and to store the additional data in cache memory, anticipating that the data might be required soon. This process speeds up reads for sequential data, but there is little improvement occurs when accessing random data.

> | No read ahead: (the default) Disables the read ahead capability.

> | Write policy: Specify the write policy for this virtual drive:

> | Write Through: In this mode, the controller sends a data transfer completion signal to the host when the drive subsystem has received all of the data in a transaction. This option eliminates the risk of losing cached data in case of a power failure.

> | Write Back with SuperCap: In this mode, the controller enables write back caching when the SuperCap is installed and charged. This option provides a good balance between data protection and performance.

> CAUTION Do not hot plug the SuperCap when power is supplied to the controller card or if there is residual charge on the SuperCap, doing so might damage both the SuperCap and the controller unit.

> NOTE The write policy depends on the status of the SuperCap. If the SuperCap is not present, is low, has failed, or is being charged, the current write policy switches to write through, which provides better data protection.

> | I/O policy: The I/O policy applies to reads on a specific virtual drive. It does not affect the read ahead cache.

> | Cached IO: In this mode, all reads are buffered in cache memory.

> | Direct IO: (the default) In this mode, reads are not buffered in cache memory. Data is transferred to the cache and the host concurrently. If the same data block is read again, it comes from cache memory.

> Cached IO provides faster processing, and Direct IO ensures that the cache and the host contain the same data.

> | Access policy: Select the type of data access that is allowed for this virtual drive.

> | Read/Write: (the default) Allow read/write access.

> | Read Only: Allow read-only access.

> | Blocked: Do not allow access.

> | Disk cache policy: Select a cache setting for this drive:

> | Enabled: Enable the disk cache.

> | Disabled: Disable the disk cache.

> | Unchanged: (the default) Leave the current disk cache policy unchanged.

DB15-000988-08-December 2013
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