IBM DS3950, Installation, User'S, And Maintenance Manual, Page: 150 / 252

Attention
Never remove a controller, power supply and fan unit, or battery unit unless
the Service Action Allowed status LED is turned on. Doing so can result in a
potential loss of data availability. If the Needs Attention LED is lit and the
associated Service Action Allowed status LED is
not lit, then you must
perform additional diagnostics before you can remove the indicated
component. Use the Recovery Guru instructions in the DS Storage Manager
Subsystem Management window or refer to the applicable component
replacement instructions in this chapter for the additional diagnostics
required in this case.
The Service Action Allowed status LED automatically turns on or off as conditions
change. Wait at least two minutes after you replace each component for the
controller to recognize the new component and update the LED status. In most
cases when a single component fails, the Service Action Allowed status LED turns
on steadily when the Needs Attention status LED is turned on for the component.
Replacing a controller
Attention: Before you replace a controller, verify the following:
v
The replacement controller part number matches the part number of the
controller to be replaced. To provide full functionality, the two controllers must
have the same cache memory capacity, same number of host ports, same types
of host ports (FC or iSCSI), and same FRU part number. Inserting a
non-compatible controller causes the controller to be placed in a lockout state by
the other controller in the DS3950 chassis.
Note: The DS3950 storage subsystem controller FRU is not compatible with the
DS4200 Express or DS4700 storage subsystem controller FRU. See the
“Parts listing” on page 164 for more information about compatible
controllers.
v
Both power supply and fan units must be connected and powered on with no
Needs Attention LEDs lit. Make sure that the Power LEDs on each of the power
supply and fan units are lit. If either of the power supply and fan units is not
optimal, replace that component before you proceed with the controller
replacement procedure.
v If you are replacing an optimal controller, first make sure that the other
controller is optimal and that the Fibre Channel path from the hosts to the other
controller is also optimal.
Each controller has a unique hardware Ethernet address, which is printed on a
label on the front.
Before you begin, ensure that you wear an anti-static wrist strap.
Use the following procedure to replace a controller in an DS3950 storage
subsystem:
1. Use the DS Storage Manager client software to print a storage subsystem
profile. Move logical drive ownership to the other controller. If the controller
you are replacing has failed but is still operating, move the failed controller to
an Offline state.
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IBM System Storage DS3950 Storage Subsystem: Installation, User’s, and Maintenance Guide