Managing RAID on Linux

Hot-Swap

All of the RAID levels that support redundancy are also capable of hot-swap. Hot-swap is the ability to removed a failed drive from a running system so that it can be replaced with a new working drive. This means drive replacement can occur without a reboot. Hot-swap is useful in two situations. First, you might not have enough space in your cases to support extra disks for the hot-spare feature. So when a disk failure occurs, you may want to immediately replace the failed drive in order to bring the array out of degraded mode and begin reconstruction. Second, although you might have hot-spares in a system, it is useful to replace the failed disk with a new hot-spare in anticipation of future failures.

Replacing a drive in a running system should not be attempted on a conventional system. While hot-swap is inherently supported by RAID, you need special hardware that supports it. This technology was originally available only to SCSI users through specially made hard drives and cases. However, some companies now make hot-swap ATA enclosures, as well as modules that allow you to safely hot-swap normal SCSI drives. For more information about hot-swap, see the Cases, Cables, and Connectors section, later in this chapter, and the Managing Disk Failures section in Chapter 7.

Warning

Although many people have successfully disconnected traditional drives from running systems, it is not a recommended practice. Do this at your own risk. You could wipe your array or electrocute yourself. ...