Selecting the Virtual Drive Settings
Keywords: Nytro SW UG

> Selecting the Virtual Drive Settings

> You can select the virtual drive 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 best to leave their default settings.

> | 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 not for any other RAID levels. New RAID 5 virtual drives require at least five drives for a background initialization to start. If there are fewer drives, the background initialization does not start.

> | Strip size: Strip sizes of 8 KB, 16 KB, 32 KB, 64 KB, 128 KB, 256 KB, 512 KB, 1024 KB, and 1 MB are supported. For more information, see the striping entry.

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

> | Always read ahead and NORA: 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 will be needed soon. This process speeds up reads for sequential data, but there is little improvement occurs when accessing random data.

> | 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 BBU (SuperCap): (the default) In this mode, the controller enables write back caching when the BBU (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 card.

> NOTE The write policy depends upon the status of the SuperCap. If the SuperCap is not present, is low, is 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 I/O: In this mode, all reads are buffered in cache memory.

> | Direct I/O: (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 I/O provides faster processing, and Direct I/O ensures that the cache and the host contain the same data.

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

> | Read/Write: (the default) Permit read/write access. This setting is the default value.

> | Read Only: Permit read-only access.

> | Blocked: Do not permit 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.

DB15-001059-00-April 2013
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