Dell PowerVault 221S (SCSI) - Manual (Page 25)

A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02
PAGE 25 11/17/2005
properly quiescent before the remove/replacement operation takes place, whereas hot
plugging can occur at any time without prior notification. Hot plugging allows the user
applications and disk activities to continue uninterrupted while maintenance or repair
actions are taking place. Warm plugging requires synchronization with the software
applications to temporarily halt disk I/O activity before the hardware is removed/replaced.
• Warm Pluggable Devices
o EMM module
o SBM module
o Terminator module
• Hot Pluggable Devices
o HDD (when disk I/O is still occurring, all activities must be halted first)
o Power
supply module
o Fan modules
• Neither Warm nor Hot Pluggable Devices
The backplane is critical for proper enclosure operations and cannot be warm or
hot plugged. Power MUST be removed from the system.
External SCSI Cables
Depending on the enclosure topology, one or two external SCSI cables can be attached
between the host system(s) and the PV22xS enclosure. Although cables may physically
look and feel the same, there are actually differences in the cable material and
construction methods used that produces different quality levels of cable. In general, the
higher the SCSI speed, the higher the quality of the cable that is required. SCSI cable
quality is governed by the American National Standards Institute, Inc. (ANSI).
Specifically, for SCSI U160 speeds, a cable must comply with the ANSI SCSI Parallel
Interface-3 (SPI-3) specification. For U320 speeds, ANSI SPI-4 must be adhered to. All
PV22xS SCSI cables purchased from Dell have been tested and comply with the ANSI
SPI-4 standard. When using existing customer cables or if the cables are purchased from
3
rd party sources, ensure the cables are approved for ANSI SPI-4 operation. Using lower
grade cabling will cause unpredictable results which can compromise the stability and
reliable operation of the PV22xS enclosure.
External SCSI Connector Types
There are two types of SCSI connectors used by the external SCSI cables. One is called
the High Density (HD) connector, also commonly referred to as a P-connector, and the
other is the Very High Density Cable Interconnect (VHDCI). Both are 68-pin connectors,
but the VHDCI has a smaller form factor, as shown in Figure 4-7. Two types of cables are
available for the PV22xS, an HD-to-HD and HD-to-VHDCI. The EMM module uses the HD
style connector where one end of the cable is attached. The other end will have either an
HD or VHDCI connector. PERC3 and PERC4 series controllers use a VHDCI connector.
Older controller cards generally use the HD connector. Always verify the controller
connector type to ensure cables will be compatible.