User`s guide

StorageWorks Status Reporting
2.1 Shelf Status
2.1 Shelf Status
The StorageWorks shelf power supply provides dc power, and the blowers provide
cooling for the controllers, cache memories, and storage devices. Failure of all
blowers on a shelf can cause devices to overheat and fail. When there is only one
power supply on a shelf, the loss of either dc voltage (+5 Vdc, +12 Vdc) will cause
the controllers, cache memories, and storage devices to malfunction. The status
of the power supplies and the the blowers is displayed on the upper power supply
LED. This status signal is available for processing by the SCSI controller or host.
The status signal, SHELF_OK, is the result of logically "anding" a signal based
on the speed of all blowers on the shelf and the "power good" signals for all power
units on the shelf. All StorageWorks shelves have at least two blowers and one
power supply providing the +5 Vdc and +12 Vdc. The BA350–EA controller and
SBB shelf has four blowers and from two to four power units.
2.1.1 SHELF_OK Signal
All StorageWorks shelves can accommodate either two ac or two dc power
supplies. Some shelves (such as the BA350–EA controller and SBB shelf) have
four blowers and can accommodate four ac or dc supplies. The loss of any dc
voltage or blower will cause the SHELF_OK signal to change from a high level
to a low level and turn off the upper power supply LED, even though there is
sufficient power for proper SBB operation. The defective blower or power supply
should be replaced as soon as possible to restore the subsystem to a redundant
capability.
Note
A single shelf can operate correctly with only one power supply furnishing
+5 Vdc and +12 Vdc.
When an error condition exists and the SHELF_OK signal level changes from
high to low, the result is as follows:
• The upper power supply LED, the Shelf Status LED, is off.
• Some controllers can process this signal and notify the host that a power
supply or blower has failed. Review the SCSI controller documentation to
determine if this signal can be processed.
2–2 StorageWorks Status Reporting