IBM DS4800 User, Installation And Maintenance Manual page 30

Figure 1. DS4800 Storage Subsystem
The storage subsystem comprises five components. The components, and the
quantity of each component in the storage subsystem, are:
v RAID controllers (two)
v Power supply-fans (two)
v Interconnect-battery unit (one)
The power supply-fans and interconnect-battery unit are located behind the front
bezel. The controllers are located in the rear of the storage subsystem. All
components are secured in the storage subsystem by quick release latches,
enabling each component to be removed by disengaging the latch and sliding the
component from the storage subsystem chassis. Figure 2 on page 9 shows the
positions of the components in the DS4800.
All DS4800 models support hot-swap RAID controllers, power supply-fans,
cache-protected batteries, and interconnect-battery units, so you can remove and
replace these components without turning off the storage subsystem.
Hot-swappable devices enable you to maintain the availability of your system while
you remove, install, or replace a hot-swap device.
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IBM System Storage DS4800 Storage Subsystem: Installation, User's, and Maintenance Guide
Attention
Refer to the component replacement sections in Chapter 5, "Replacing
components," on page 133, or refer to the DS4000 Storage Manager
Recovery Guru, for instructions and prerequisites before performing any CRU
replacements. Failure to meet prerequisites or follow replacement instructions
might result in a loss of data access.