Silicon Graphics InfiniteStorage 4000 Series, Настройка и обслуживание

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202 Recovery Operations
ATTENTION Possible loss of data access
– Never remove a component that has a
Service Action Required indicator light on unless the Service Action Allowed
indicator light is on.
If a component fails and must be replaced, the Service Action Required indicator light
on that canister comes on to indicate that service action is required, provided no data
availability dependencies or other conditions exist that dictate the canister should not
be removed. The Service Action Allowed indicator light automatically comes on or
goes off when conditions change. In most cases, the Service Action Allowed indicator
light comes on steadily when the Service Action Required indicator light comes on
for the canister.
If the interconnect-battery canister must be replaced, the Service Action Allowed
indicator light does not come on automatically. Before the Service Action Allowed
indicator light on the interconnect-battery canister can come on, you must place
controller canister in slot B into Service mode. This action routes all control and I/O
activity through one controller to help make sure that data access is maintained while
the interconnect-battery canister is removed. The Service Action Allowed indicator
light comes on after the new canister has been installed.
The ability to remove a canister depends on the data availability dependencies of the
controller tray or the controller-drive tray. The Service Action Allowed indicator light
does not come on if removing a canister jeopardizes data on the drive trays or current
I/O activity. An example of limiting when you can remove a canister is when one
controller canister has a Service Action Required indicator light on. You cannot
remove the other controller canister (the Service Action Allowed indicator light does
not come on), because doing so would jeopardize the data either on the drive trays or
transitioning through the controllers.
A less obvious example is when the power supply for the controller canister in slot A
has failed, and the controller canister in slot B has failed. Removing the controller
canister in slot B before replacing the failed power-fan canister causes the controller
canister in slot A to lose power, which results in a loss of data access. This action
occurs because power distribution from each power-fan canister is through the
controller canister that is physically connected to that power-fan canister.
So, in the preceding example, these actions occur:

The power-fan canister has both its Service Action Required indicator light and
its Service Action Allowed indicator light on.

The controller canister in slot B has only its Service Action Required indicator
light on, but its Service Action Allowed indicator light is off.

After the failed power-fan canister has been replaced, the Service Action
Allowed indicator light comes on for the controller canister in slot B.
The following table shows when the Service Action Allowed indicator light does not
come on for each canister (the indicator light is suppressed). An
X
in a table cell
indicates that service is not allowed, therefore the Service Action Allowed light does