Users Guide

NOTE: Write-through is the default write policy setting when cluster mode is enabled.

• Write Cache Enabled Protected — The controller writes data to the write cache before writing data to the physical disk. Because it

takes less time to write data to the write cache than it does to a disk, enabling write cache can improve system performance. After

data is written to the write cache, the system is free to continue with other operations. The controller, in the meantime, completes the

write operation by writing the data from the write cache to the physical disk. The Write Cache Enabled Protected policy is available

only if the controller has a functional battery. The presence of a functional battery ensures that data can be written from the write

cache to the physical disk even when there is power failure.

NOTE: Storage Management does not allow you to select the Write Cache Enabled Protected policy for controllers that

do not have a battery. This restriction protects a controller without a battery from the data loss that may occur in the

event of a power failure. When using the Create Virtual Disk Advanced Wizard on a controller without a battery, the

wizard either displays Write Cache Disabled as the only available option or the wizard does not display any option for write

policy.

• Write Cache Disabled — This is the only option available when the controller does not have a functional battery.

Cache Policy

Does my controller support this feature? See Supported Features.

The Direct I/O and Cache I/O policy apply to readings on a specic virtual disk. These settings do not aect the read-ahead policy. The

cache policies are:

• Cache I/O — Species that all reads are buered in cache memory.

• Direct I/O — Species that reads are not buered in cache memory. When using Direct I/O, data is transferred to the controller cache

and the host system simultaneously during a read request. If a subsequent read request requires data from the same data block, it can

be read directly from the controller cache. The Direct I/O setting does not override the cache policy settings. Direct I/O is the default

setting.

NOTE

: Cache policy is not supported on controllers that do not have a battery.

Disk Cache Policy

Does my controller support this feature? See Supported Features.

NOTE

: The Disk Cache Policy feature is not supported on solid-state disks (SSDs) and on SAS 12 Gbps Adapter.

The Disk Cache Policy feature is supported on Non-RAID SAS/SATA physical disks (HDDs) connected to PERC hardware controllers and

on RAID SAS/SATA physical disks connected to Software RAID S130 controller. This feature is not dependent on the controller mode and

can function as usual when the controller is running in RAID or HBA mode.

Set the physical disk caching policy of all members of a virtual disk by enabling the Disk Cache Policy. When this feature is enabled, the

physical disk writes data to the physical disk cache before writing it to the physical disk. Because it is faster to write data to the cache than

to a disk, enabling this feature improves system performance.

The following are the disk cache policy options for Non-RAID disks connected to a PERC hardware controller:

• Enabled — Disk Cache Policy is enabled.

• Disabled — Disk Cache Policy is disabled.

• Unchanged — The disk uses the default write cache mode.

NOTE

: The Unchanged option is applicable only for PERC 9 hardware controllers with the latest rmware

version.

NOTE: If you want to revert the Disk Cache Policy settings of the physical disks to the factory default settings, then you

must restart the server.

The following are the disk cache policy options for RAID disks connected to Software RAID S130 controller:

Controllers