Infortrend RAID Controller Manual

Configuration A is a large logical drive and takes a long time to
rebuild. All of the 24 members will be involved during the rebuild
process. In Configuration B, the time span is shorter because only a
maximum of 6 drives will participate when rebuilding any of the
logical drives.
c) Channel Failure Protection: A channel failure will cause multiple
drives to fail at the same time and inevitably lead to a fatal failure.
Using a logical volume with drives coming from different drive
channels can get around this point of failure. Channel failure may
sometimes result from absurd matters like a cable failure.
Figure 2 - 18 Logical Volume with Drives on Different
Channels
Logical
Volume
Logical Volume
24 drives, 4 redundancy drive
RAID 5
Logical
Drive
RAID 5
Logical
Drive
RAID 5
Logical
Drive
RAID 5
Logical
Drive
Configuration C - One logical volume with 4 logical drives
Functional Description 2-13
CH1
CH1/ID3
CH2
CH3
CH4
CH5
CH6
CH1/ID0 CH2/ID0 CH3/ID0 CH4/ID0 CH5/ID0 CH6/ID0
CH1/ID1 CH2/ID1 CH3/ID1 CH4/ID1 CH5/ID1 CH6/ID1
CH1/ID2 CH2/ID2 CH3/ID2 CH4/ID2 CH5/ID2 CH6/ID2
CH2/ID3 CH3/ID3 CH4/ID3 CH5/ID3 CH6/ID3
As illustrated above, should one of the drive channels fail, each
logical drive loses one of its members. Logical drives will still be
capable of normal operation. Data remains intact and the rebuild can
be performed after the failed channel is recovered. No access
interruptions to the logical volume will be experienced on the host
side.
Spare drives in a logical volume?
A Local Spare can not be assigned to a Logical Volume. If a drive
fails, it fails as a member of a logical drive; therefore, the controller
allows Local Spare's assignment to logical drives rather than logical
volumes.
Limitations:
The logical volume cannot have any logical drive stated as "fatal
failed.” If there is any failed drive in any of the member logical drives
(of a logical volume), controller will start to rebuild that logical drive.