Asus DS300 G2 Series, Руководство пользователя

Страница: 200 / 262

DS300f G2 Series User Manual
194
data from the revertible spare drive.
See the example on the following pages.
e
xAMPle
Following is an example to explain the Transition function.
In the example above, there is a four-drive RAID 5 disk array and a global spare drive. Physical drives 1, 2, 3,
and 4 belong to the disk array. Physical drive 5 remains unconfigured. Physical drive 6 is a revertible spare drive.
If a physical drive fails in a disk array and there is a spare drive of adequate capacity available, the controller
automatically rebuilds the array using the spare drive. In this example, physical drive 3 failed and the array is
rebuilt using physical drive 6, the revertible spare drive.
When the rebuild is complete, the spare drive has replaced the failed drive. In this example, failed drive 3 was
replaced by spare drive 6. The disk array now consists of physical drives 1, 2, 4, and 6.
There is no spare drive at this moment. Even if physical drive 5 is of adequate capacity, it has not been
designated as a spare, therefore the controller cannot use it as a spare.
A
utoMAtic
t
rAnsition
At this juncture, you would replace the failed drive in slot 3 with a new one of the same or greater capacity.
When the ASUS DS300f G2 controller detects the new drive in slot 3, the controller:
• Automatically transitions the data on drive 6 to drive 3
• Returns drive 6 to spare status
When the Automatic Transition is finished, physical drives 1, 2, 3, and 4 belong to the disk array and physical
drive 6 is a revertible spare drive. The original configuration is restored.
M
AnuAl
t
rAnsition
If you wanted to use the drive in slot 5 as a member of the disk array, rather than the drive in slot 3, you would
run the Transition function manually.
When the Manual Transition is finished, physical drives 1, 2, 4, and 5 belong to the disk array and physical drive
6 is a revertible spare drive.
At this point, you would replace the drive in slot 3. The new drive in slot 3 remains unconfigured until you assign
it to a disk array or as a spare.
raId C
ontrollers
RAID controller technology includes;
• "LUN Affinity" on page 194
• "ALUA" on page 194
• "Cache Policy" on page 195
• "Preferred Controller ID" on page 196
• "Power Saving" on page 196
• "Capacity Coercion" on page 196
lun a
ffInIty
ASUS DS300f G2 subsystems with dual RAID controllers include a LUN Affinity feature. Normally, either controller
can access all logical drives. LUN Affinity enables you to specify which controller can access each logical drive.
Use this feature to balance the load of your logical drives between the two controllers.
To use LUN Affinity you must:
• Have two RAID controllers in the subsystem.
• Set the redundancy type to Active-Active.
See "Making Subsystem Settings (CLU)" on page <?>.
• Enable LUN Affinity.
See "Making Subsystem Settings (CLU)" on page <?>..
On subsystems with two RAID controllers, when Cache Mirroring is disabled, LUN Affinity is enabled automatically.
alua
ASUS DS300f G2 supports Asymmetric Logical Unit Access (ALUA) on Linux OSes. ALUA is a multhipathing
tool. It enables an initiator (your host PC or server) to discover target port groups that provide a common
failover / failback behavior for your LUNs. ALUA enables the host to see which paths are in an optimal state and
which are not.
To use ALUA you must:
• Have two RAID controllers in the subsystem.