How RAID handles disk failures

Disk failure without a hot spare disk

About this section

This section describes how the filer reacts to a disk failure when a hot spare disk is not available.

Filer runs in degraded mode

If a disk fails, the filer continues to run without losing any data but performance is somewhat degraded.

Caution
Replace the disk as soon as possible, because a second disk failure could cause the filer to lose the entire file system.

Filer logs warning messages in /etc/messages

The filer logs a warning message in the /etc/messages file on the root volume every hour after a disk fails.

Filer shuts down automatically after 24 hours

To ensure that you notice the failure, the filer automatically shuts itself off in 24 hours, by default, or in a period you set with the raid.timeout option with the options command. You can restart the filer without fixing the disk, but it continues to shut itself off periodically until you repair the problem.

Filer sends messages about failures

Check the /etc/messages file on the root volume once a day for important messages. You can automate checking this file from a remote host with a script that periodically searches the file and then alerts you.

Alternatively, monitor autosupport messages. Data ONTAP sends autosupport messages when a disk fails.

Filer reconstructs data after disk is replaced

After you replace a disk, the filer detects the new disk immediately and uses it. The filer starts file service and reconstructs the missing data in the background to minimize interruption to service.