34 en | Subsystem Connection and Operation RAID Subsystem DVA-08K | Installation Manual
F.01U.027.797 | V2 | 2008.08 Bosch Security Systems
5 Subsystem Connection and Operation
This chapter introduces sample topologies, configuration options and server connections for
the RAID subsystems and discusses both the power on and power off procedures.
5.1 Basic Configuration Rules
When you are configuring your storage subsystem, follow these basic rules:
• Using a mix of LVD and legacy devices, such as devices using single-ended signaling, is
not recommended. Use LVD terminators if all your devices support LVD signaling. Please
refer to the documentation provided with your SCSI devices to avoid possible conflicts.
• When selecting the number of hard drives to be included in a logical configuration that
should be presented through the host channels, the transfer rates and the mechanical
performance of the hard disks should be considered. The combined bandwidth of the
two SCSI host channels is 640MB/s, sufficient for most applications. If properly config-
ured, combining subsystems or drive enclosures may increase the number of drives and
help to bring out the most of IOPs performance.
• If you consider cascading multiple enclosures, considerations may include the character-
istics of your I/O load. Select the correct combination of optimization mode and a spe-
cific RAID level.
• An optimal configuration is always a compromise among different factors. For instance, a
large array with many drive members may be more efficient, but the chance of failing a
member is also increased.
• The drives in the same logical array should have the same capacity; it is preferred that all
the drives in the enclosure have the same capacity.
• A spare drive should have a minimum capacity equivalent to the largest drive that is to be
replaced. If the capacity of the spare is less than the capacity of the drive to be replaced,
then the controller will not proceed with the failed drive rebuild.
