IBM EXP400 Type 1733, Руководство по техническому обслуживанию и ремонту

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unit configurations. If the average load on your expansion unit is less than 500
watts and a problem occurs with one of the power supplies, the other power
supply can meet the power requirements.
Expansion unit model 2RX uses a dual dc input power system. For detailed
information about working with the dual dc input power system, see Chapter 3,
“Information for the -48 volt dc power model,” on page 19.
v ServeRAID
™
support
Your expansion unit supports servers with ServeRAID adapters to create
redundant array of independent disks (RAID) configurations.
v Clustering support
Twin-tailed clustering support is a feature of the expansion unit. Clustering is a
way to share SCSI buses and hard disk drives between two SCSI controllers to
provide redundancy of SCSI controllers and servers. This redundancy is
important if one of the controlling servers fails. If a hardware component fails
after clustering is set up, another server will take ownership of the hard disk
drives.
With twin-tailed clustering, you can connect two IBM ServeRAID controllers to an
expansion unit. In the twin-tailed clustering environment, you can use dual-host
controllers cabled separately to the expansion unit; however, only a single bus of
13 drives is supported. Each SCSI device on a SCSI bus must have a unique ID.
Service tip: If you use IBM ServeRAID controllers in a cluster configuration, the
termination-power LED on the back of the expansion unit is useful. The
ServeRAID controller provides the signal for termination power. If the termination
power LED is not lit, it indicates that a particular expansion unit is not attached to
a controller that is turned on. Make a note of which expansion unit is attached to
which server before the hardware is serviced.
Clustering requires additional hardware and specialized software. For more
information, go to http://www.ibm.com/pc/ww/eserver/xseries/clustering/.
Chapter 1. General information
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