Compaq Infortrend Manuale Utente

minimized to reduce the possibility of having two drives to fail at
the same time.

Configuration A is a large logical drive and takes a long time to
rebuild.  All members will be involved during the rebuild process.
In Configuration B, the time span is shorter because only 6 members
will participate when rebuilding any of the logical drives.

c) Channel Failure Protection: Channel failure may sometimes
result from absurd matters like a cable failure.

   

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.

Configuration C - One logical volume with 4 logical drives

Logical

Volume

CH1

CH1/ID0

CH1/ID1

CH1/ID2

CH1/ID3

CH3

CH3/ID0

CH3/ID1

CH3/ID2

CH3/ID3

CH4

CH4/ID0

CH4/ID1

CH4/ID2

CH4/ID3

CH5

CH5/ID0

CH5/ID1

CH5/ID2

CH5/ID3

CH2

CH2/ID0

CH2/ID1

CH2/ID2

CH2/ID3

CH6

CH6/ID0

CH6/ID1

CH6/ID2

CH6/ID3

As illustrated above, should one of the drive channels fail, each
logical drive loses one of its members.  Logical drives still have the
chance to rebuild its members.  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 from the host
side.

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.