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Maintenance 3-13
Compaq Confidential – Need to Know Required
Writer: Bob Young Project: RAID Array 3000 Pedestal Storage Subsystem Hardware User’s Guide Comments:
Part Number: EK-SMCPO-UG. C01 File Name: d-ch3 Maintenance.doc Last Saved On: 12/4/00 1:50 PM
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.
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 Compaq.
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.