Compaq RAID Array 4100 User Manual page 71

Follow these guidelines when replacing drives:
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Never remove more than one drive at a time. When you replace a
drive, the controller uses data from the other drives in the array to
reconstruct data on the replacement drive. If you remove more than one
drive, a complete data set is not available to reconstruct data on the
replacement drive(s) and permanent data loss could occur.
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Never remove a working drive. The amber Drive Failure LED on the
drive carrier indicates drives that have been failed by the controller.
Permanent data loss will occur if a working drive is removed while
replacing a failed drive. See Figure 4-27.
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Never remove a drive while another drive is being rebuilt. A drive's
Online LED flashes green while it is being rebuilt. A replaced drive is
rebuilt from data stored on the other drives. See Figure 4-27.
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Never turn a disk enclosure off while the initiator or controller is
powered on or active. Doing so may cause the initiator or controller to
mark the drives as "failed." This could result in permanent data loss.
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If the system has an online spare drive, wait for it to complete
rebuilding before replacing the failed drive. When a drive fails, the
online spare becomes active and begins rebuilding as a replacement
drive. After the online spare has completed Automatic Data Recovery
(The Online LED will be continuously lit), replace the failed drive with
a new replacement drive. Do not replace the failed drive with the online
spare. See Figure 4-27.
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If you replace a drive while the system is off, it may be necessary to
rebuild the replaced drive. Follow the instructions on the screen or the
instructions outlined in the system's reference guide.
Troubleshooting 4-23