Specifications

SCSI to SATA RAID Subsystem | Administrator’s Manual RAID Functions: Introduction | en 21
Bosch Security Systems F.01U.027.802 | V1 | 2006.11
Fig. 1.18 Logical Volume with Drives on Different Channels
As illustrated above, if one of the drive channels fails, each logical drive loses one of its mem-
bers. 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.
1.6.2 Can Spare Drives Assigned to a Logical Volume?
A Local Spare cannot be assigned to a Logical Volume. If a drive fails, it fails as a member of a
logical drive; therefore, the controller allows a Local Spare's assignment to logical drives
rather than logical volumes.
1.6.3 Limitations
The logical volume can not have any logical drive stated as "fatal failed.” If there is any failed
drive in any of its member logical drives, the controller will start to rebuild that logical drive. If
any of the member logical drives fail fatally, the logical volume fails fatally and data will not be
accessible.
To avoid a logical volume failure:
1. Logical drives as members of a logical volume should be configured in RAID levels that
provide redundancy, i.e., - RAID levels 1 (0+1), 3 or 5.
2. Rebuild the logical drive as soon as possible whenever a drive failure occurs. Use of local
spares is recommended.
3. A logical drive should be composed of physical drives from different drive channels. Com-
pose the logical drive with drives from different drive channels to avoid the fatal loss of
data caused by bus failure.
1.6.4 Partitioning the Logical Drive or Partitioning the Logical Volume?
Once a logical drive has been divided into partitions, the logical drive can no longer be used as
a member of a logical volume. The members of a logical volume should have one partition only
with the entire capacity.
If you want to use a partitioned logical drive for a logical volume, delete the other partitions in
this logical drive until there remains one partition only with the entire capacity. Note that
deleting the partition of the logical drive will also destroy all data. Data should be backed up
before making partition configurations.