Dell PowerVault 221S (SCSI) - Manual (Page 19)

A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02
PAGE 19 11/17/2005
4. PV22xS Enclosure Overview
The PV22xS SCSI Enclosure provides three configuration topologies, also referred to as
modes, which are end-user configurable:
Joined , Split , and Cluster topologies, as shown
in Figure 4-1. A 3-position switch located on the Split Bus Module (SBM) sets the desired
enclosure topology. Each of these topologies will be further explained in more detail
below. The configuration will not take effect until the enclosure is power cycled which is
designed to protect from accidental topology changes. SCSI Enclosure Services (SES)
management features are an integral part of the enclosure. SES provides a unique set of
features to monitor critical environmental variables such as temperature and power status.
Figure 4-1 PV22xS Topologies
Joined Bus Topology
This is the simplest topology of operation providing access to all 14 hard drives on one
shared SCSI bus. Only one cable must be attached between the server and the primary
Enclosure Management Module (EMM) in the enclosure. If operating with two EMM
modules, which provide redundant SES services, a second cable should not be attached
to the secondary EMM. There can only be one physical path from the enclosure to the
server. Attaching a second cable is not supported and may lead to SCSI bus address
contention. If SES redundancy is not required, a Terminator module can be substituted in
place of secondary EMM.