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20 9176/D173 D
ISK SUBSYSTEM - SITE PREPARATION GUIDE
9176/D173 Disk Subsystem Current Calculations
With the 9176 Disk Controller (at 220v) pulling one ampere and the 9170 or D173 each
pulling 1.8 amperes, a rackmount cabinet with one controller and ten disk arrays would
draw a total of 19 amperes. These amps are supplied by two grids of the power distribution
unit (PDU), with each grid rated at 16 amps. The lower grid would supply one controller
and five disk arrays (1 + 1.8 + 1.8 + 1.8 + 1.8 + 1.8) for a total of 10 amps, and the upper
grid would supply the remaining five disk arrays (5 times 1.8) for a total of 9 amps. A 30
drive D173 Disk Subsystem (with its 20 amp PDU) pulls 5.4 amps (11 amps at 110v).
9176/D173 Disk Subsystem Maximum Operating Power
Calculations
When calculating maximum operating power (the time just after the start-up power time
zone), use 329 VA for the 9176 Disk Controller and 495 VA for the 9170 Disk Array and
D173 Controller Disk Array as shown in Table 10 and Table 11.
For example, if calculating for a fully configured 9176 Disk Subsystem with two hundred
72 Gigabytes drive (i.e. twenty 9170 Disk Arrays), one would add the controller’s 0.329
KVA to twenty times the disk array’s 0.495 KVA. The formula becomes:
0.329 + 20 (0.495) = 0.329 + 9.90 = 10.23 KVA
The maximum operating power consumption, therefore, for a fully configured 14.4
Terabyte 9176 Disk Subsystem (1 disk controller and 20 disk arrays) is 10.23 KVA.
Knowing that 10.23 KVA is the maximum operating power, we can figure the current for
the two cabinets as follows.
•
a 240 volt source would draw 42.6 amps
•
a 220 volt source would draw 46.5 amps
•
a 200 volt source would draw 51.1 amps.
NOTE The ratings of the individual drive modules (pulling 1.4 amps at 5 volts DC and
1.7 amps at 12 volts DC) mean that the 9170 power supplies provide this current
(via the midplane) to all of the drive modules. The AC current drawn by the
9170 power supplies is essentially what is documented in Table 10 and Table 11.
Basically, the "load" is the controller modules, fan modules, and all ten drive
modules. Each of these 9170 components adds up to a combined maximum of
2.1 amps of AC current drawn at 240 volts. Note also that the relationship
between AC and DC power requires one to use the .707 or 1.414 conversion
factors. Use this to interpret such statements as: (0.495 kVA or 350.0 W).