DEC DS-HSZ22-AA, User Manual

Page: 64 / 94

RAID Array 3000 Pedestal Enclosure
3–12 EK–SMCPO–UG. A01
3.6.14 Replacing the UPS
Proceed as follows to replace the UPS:
1. Ensure the UPS power switch is set to off.
2. Disconnect the pedestal power cord from the UPS.
3. Disconnect the UPS power cord from the wall outlet.
4. Disconnect the signal control cable from the UPS
5. Install the replacement UPS and reconnect the power cords and the signal
control cable.
6. Set the UPS power switch to on and then power up the pedestal.
3.7 Differential/Wide UltraSCSI Bus
The reliability of data transfers on a SCSI bus depends on the following factors:
•
The bus transmission rate
•
The maximum SCSI bus length (a function of bus type, the transmission rate,
and the use of SCSI bus converters)
•
The total length of the SCSI bus (as measured from the host bus terminator to
the subsystem terminator)
•
MT/s (mega-transfers per second) is the repetitive rate at which words of data
are transferred across a bus. The number of megabytes per second (MB/s) is
determined by the bus width (8 or 16-bit) and the number of bytes per word
(1 or 2, respectively)
Table 3–2 lists the maximum SCSI bus lengths and the longest SCSI
cables recommended by DIGITAL.
NOTE
Because the bus length includes the cable plus
the backplane distance inside the enclosure, the
recommended maximum cable lengths listed
are
not the same as the maximum bus length.