Configure Cache
Clicking
System Admin
takes you to the
Configure Cache
page, which allows you to configure settings for
the unit’s cache memory.
Cache memory holds data that is being written to one or more disks, which enables the RAID Controller to
confirm that a command has been completed before the data has been written to disk.
In the event of a power interruption, when the power is restored to the unit the RAID Controller will
automatically complete any write operations using the data held in the cache.
Figure 3-137:
Configure Cache
page
The
Configure Cache
page displays the current cache settings and lets you configure them.
Current write cache state
shows whether the cache is currently enabled or disabled, mirrored, and in
streaming mode, plus its “force unit access” (FUA) status and the size of the cache in megabytes (MB) for
each RAID Controller.
Manually override current write cache status
: Normally, when the user enables or disables the cache,
the unit must be rebooted for it to take effect. Using this check box, you can force the cache to become
Enabled
(if it is disabled) or
Disabled
(if it is enabled) without rebooting the system.
Desired write cache state
: By default, this is
Enabled
.
Allow attached host to override write cache configuration
: Some hosts can issue commands that
force the cache to not be used. When this box is unchecked (the default), the system does not allow this.
Ignore force unit access (FUA) bit
: Some SCSI commands contain a “force unit access” (FUA) bit,
which forces the unit to bypass cache memory and perform read and write operations directly from and to
the disks. When this box is checked, the unit ignores the FUA bit and always uses the cache memory for
command execution.
Enable cache mirroring
: On Nexsan High-Density Storage systems in a dual-controller active-active
failover mode (see
on page 198), this setting is on by default. It tells the system to duplicate
the contents of the cache of one RAID Controller to the other, thus ensuring that cache contents are not
lost in the event of a controller failure.
Chapter 3: The Graphical User Interface — System Administration
Nexsan High-Density Storage
User Guide
189