AMCC 3WARE 720-0138-00 - Manual (Page 39)

About Controller Policies
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About Controller Policies
The following policies affect all units and drives on a controller and can be
adjusted as appropriate for your equipment. Controller policies are shown at
the bottom of the Controller Settings page.
• Auto Rebuild. Determines whether the Auto Rebuild policy is enabled or
disabled. When disabled, degraded units can only be rebuilt with
designated spares. When enabled, the controller firmware will attempt to
rebuild a degraded unit if there is no spare, using either an available drive
or a failed drive.
• Auto-Carving. Determines whether the auto-carving policy is enabled or
disabled. When it is enabled, any unit larger than a specified size (known
as the carve size) is broken into multiple volumes that can be addressed
by the operating system as separate volumes. The default carve size is 2
TB.
This auto-carving feature is sometimes referred to as multi-LUN, where
each volume that is created is referred to as a “LUN.”
• Carve Size. Sets the size for dividing up units into volumes when Auto-
Carving is enabled. This setting can be between 1024 and 2048 GB.
Some additional policies can be set at the unit level. For more information,
see “Setting Unit Policies” on page 44.
Setting the Auto Rebuild Policy
The Auto Rebuild policy determines how the controller firmware will attempt
to rebuild degraded units.
When Auto Rebuild is disabled, only spares will be automatically used to
rebuild degraded units. When Auto Rebuild is enabled, the firmware will
select drives to use for automatically rebuilding a degraded unit using the
following priority order.
• Smallest usable spare.
• Smallest usable unconfigured (available) drive.
• Smallest usable failed drive.
Enabling Auto Rebuild allows you to add a drive to the controller and have it
be available for a rebuild, without having to specify it as a spare.
With Auto Rebuild enabled, if you accidentally disconnect a drive (causing
the controller to see it as a failed drive) and then reconnect it, the controller
will automatically try to use it again.