HP SureStore E Disk Array 12H User's and Service Manual (C5445-90901, September 1999)

Appendix D. Back-to-Back Racking
Product Description
238
Racking
Other Documentation
This document constitutes an overview of the back-to-back racking installation. Detailed installation
instructions accompany the other kits. Other documentation includes:
E7687-90001 7687A HP 200-240V Exhaust Fan Assembly Installation Guide
A4915-96000 HP SureStore E Disk Array 12H Power Upgrade Kit, Quick Installation Guide
E7670-90001 Power Distribution Unit Kit Installation Instructions
C2785-90002 Computer Support Rail Kit Installation Instructions
Features
The exhaust fan module contains three cooling fans. The module operates in a redundant power
configuration; that is, the module draws power from two of the rack’s PDUs (one fan draws from one PDU,
the other two fans draw power from another PDU). If power from one of the PDUs fails, one or two fans
drawing power from the other PDU will continue to provide cooling for the rack. If one of the fans fails
physically, the remaining fans in the fan module will continue to cool the rack. However, after a fan failure,
it is recommended that the failed unit be replaced within 48 hours, so that disk drive reliability is not
compromised.
LED Indicators
Front panel indicator LEDs show normal operation and fan failures. Power failures are indicated by no
LEDs being lit.
Power Redundancy
The disk arrays in the rack can be configured for power redundancy. In redundant mode, if power to one of
the rack’s PDUs fails, the other two PDUs will continue to power all disk array units. To provide power
redundancy, each PDU must be connected to a separate, dependable (or UPS) power source.