Users Guide

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:
• Default — The disk uses the default write cache mode.
• Enabled — Disk Cache Policy is enabled.
• Disabled — Disk Cache Policy is disabled.
• Inconsistent — The disk cache policy is not uniform across all the physical disks in the virtual disk. For example, if a virtual disk
contains three physical disks; the disk cache policy of the rst physical disk is Enabled, the second physical disk is Disabled, and the
third physical disk is Default. Then the disk cache policy state for the virtual disk is displayed as Inconsistent.
Controllers
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