IBM DS3500 Installation, User's, And Maintenance Manual page 109

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Attention: Turning off and turning on power without waiting for the storage subsystem disk drives to
spin down can damage the drives and might cause data loss. Always wait at least 70 seconds after you
turn off the power before you turn on the power again.
Power-off overview
Review the following information before you continue with the power-off procedure:
Turn off the power to each device according to the following shutdown sequence:
1. Turn off power to the host before the storage subsystem. If the host must stay powered-on to support
a network, see the operating-system documentation for information about disconnecting the storage
subsystem logical drives from the host before the storage subsystem is powered-off.
2. Turn off power to the storage subsystem before you turn off power to the storage enclosures. Turn off
both power-supply switches on the rear of the storage subsystem.
3. If there are enclosures with dc power supplies in your storage subsystem, turn off the -48V disconnect
devices after turning off the power-supply switches.
4. Turn off power to other supporting devices (for example, management stations).
Note: You do not have to perform this step if you are servicing only the storage subsystem.
Chapter 4. Operating the storage subsystem and storage enclosure
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