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recommended that you connect the two UPS units for the pair to different
independent electrical power sources. This reduces the chance of an input power
failure at both UPS units.
The UPS must be in the same rack as the nodes. Ensure that you are following the
UPS guidelines that are provided in Table 1.
Table 1. Uninterruptible power supply support guidelines
Number of nodes
2
4
6
8
Attention:
1. Do not connect the uninterruptible power supplies to an input power
source that does not conform to standards.
2. Each UPS pair must power only one SAN Volume Controller cluster.
Each UPS includes power (line) cords that connect the UPS to either a rack power
distribution unit (PDU), if one exists, or to an external power source. Each UPS
power input requires the protection of a UL-approved (or equivalent) 250 volt, 15
amp circuit breaker.
The UPS is connected to the SAN Volume Controllers with a power cable and a
signal cable. To avoid the possibility of power and signal cables being connected to
different UPS units, these cables are wrapped together and supplied as a single
field replaceable unit. The signal cables enable the SAN Volume Controllers to read
status and identification information from the UPS.
Each SAN Volume Controller monitors the operational state of the UPS to which it
is attached. If the UPS reports a loss of input power, the SAN Volume Controller
stops all I/O operations and dumps the contents of its DRAM to the internal disk
drive. When input power to the UPS is restored, the SAN Volume Controllers restart
and restore the original contents of the DRAM from the data saved on the disk
drive.
A SAN Volume Controller is not fully operational until the UPS battery charge state
indicates that it has sufficient capacity to power the SAN Volume Controller long
enough to permit it to save all its memory to the disk drive in the event of a power
loss. The UPS has sufficient capacity to save all the data on the SAN Volume
Controller at least twice. For a fully-charged UPS, even after battery capacity has
been used to power the SAN Volume Controllers while they save DRAM data,
sufficient battery capacity remains to let the SAN Volume Controllers become fully
operational as soon as input power is restored.
Note: Under normal circumstances, if input power is disconnected from the UPS,
the SAN Volume Controller connected to that UPS performs a power down
sequence. This operation, which saves the configuration and cache data to
an internal disk in the SAN Volume Controller, typically takes about three
minutes, at which time power is removed from the output of the UPS. In the
event of a delay in the completion of the power down sequence, the UPS
Number of uninterruptible
power supply 5125 units
2
2
4
4
Chapter 2. Overview of the uninterruptible power supply
Number of uninterruptible
power supply 5115 units
2
4
6
8
17
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