Dell PowerVault 221S Optimizing Dell SCSI Solutions - Page 25

A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 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 3rd 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. PAGE 25 11/17/2005