45xx Modular Disk Subsystem Manual for G-Series Releases

Introduction
45xx Modular Disk Subsystem Manual for G-Series Releases—142466
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455DS Decision-Support Disk Module
For improved performance, be sure to balance the disk configuration so that all
processors are equally busy. For example, one processor should not be the primary
processor for all mirrored volumes. For more details on disk-load balancing, see the
SCF Reference Manual for the Storage Subsystem.
455DS Decision-Support Disk Module
The 455DS decision-support disk module eliminates the redundant power supply and
redundant BEB that are found in the 455mod8 fault-tolerant disk module. As a result,
the 455DS module is more cost-effective but provides less fault tolerance.
Having both disk drives of a mirrored volume within a single 455DS module is not
recommended. If data availability is an important consideration and if you have more
than one module installed on your system, consider configuring the primary and mirror
disk drives in separate modules. This configuration can help maximize the availability
of data on your most critical disks if access to one module fails.
Upgrading a 455DS Module to a 455mod8 Module
You can change a 455DS decision-support disk module to a 455mod8 fault-tolerant disk
module. Contact your service provider to order an upgrade kit (product number 455UP).
The upgrade kit can also be installed by your service provider.
Figure 1-9. Four-Adapter Configuration
002CDT .CDD
BEB
BEB
BEB
BEB
SAC 4
SAC 3
SAC 2
SAC 1
6760 Adapter
SAC 4
SAC 3
SAC 2
SAC 1
6760 Adapter
SAC 4
SAC 3
SAC 2
SAC 1
6760 Adapter
SAC 4
SAC 3
SAC 2
SAC 1
6760 Adapter
Mirror Backup
Mirror
Primary
Backup
45xx Disk Module
45xx Disk Module