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RAID Subsystem DVA-08K | Installation Manual
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:
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5.2
SCSI Connection Overview
The SCSI host ports connect to SCSI-320 host adapters (HBA) that comply with 320MB/s
transfer rate and SCSI-3 protocol, best capable of 64-bit/133MHz PCI operation. Connection
of the subsystem's SCSI ports is flexible. For example, you may use the two VHDCI ports of a
dual-stacked connector to connect a host channel to two separate, clustered servers. If high
availability or path redundancy software is applied, a total of 4 VHDCI ports are available for
cross-linking to host adapters. As long as access contention is not of the concern, host con-
nection can be very flexible. In the following sections, configuration diagrams will be provided
to illustrate the possible uses of the subsystem in different application environments.
Note that these configurations are only recommendations and do not intend to impose limita-
tions such as the use of high availability software or cascading multiple enclosures. The same
configuration principles applies to the subsystem.
The RAID subsystems support 2 SCSI host channels and 2 dual-stack connectors featuring
support for SCSI-320 protocol (also known as Ultra-320), the latest iteration of the SCSI drive
interface standard. The SCSI-320 enables maximum data transfer rates up to 320MB/second
per channel from host computers to the subsystems or expansion systems. This is twice the
bandwidth as the Ultra160 standard, allowing you optimal performance and flexibility with
configuring storage applications.
5.2.1
SCSI Cables
One SCSI cable is required with each subsystem for host connection. If you wish to connect
the second host channel, a second cable is required. Use only high quality SCSI-320 cables
Bosch Security Systems
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.
Subsystem Connection and Operation | en
F.01U.027.797 | V1 | 2006.05
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