Disk and File System Management 3-5
encourage you to replace the failed disk. You can change the amount of time from
24 hours to another value using the raid.timeout option to the options
command.
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The effects of a disk failure on filer operation depend on whether the filer has a hot
spare disk.
Without a hot spare disk: If the filer is not equipped with a hot spare disk, after a
disk fails the filer enters a state called degraded mode. In this state, the RAID fea-
ture enable the filer to continue to run without losing data (although the filers
performance is affected). Replace the failed disk as soon as possible because a sec-
ond disk failure in the same RAID group causes the entire file system to be lost.
When a disk fails, the filer logs a warning message in the /etc/messages file and to
the system console every hour, notifying you of the number of hours before the sys-
tem shuts down.
The shutdown ensures that you notice the disk failure. You can restart the filer with-
out fixing the disk, but the filer continues to shut itself off at the specified intervals
until you repair the problem.
By default, the filer shuts down after 24 hours. You can change this time interval using
the option raid.timeout command; the argument is the time, in hours, that the
system runs before automatic shutdown.
The system shuts down after the specified period if it is running in degraded mode. A
filer is in degraded mode if either of the following conditions exist:
One disk in any RAID group has failed.
The batteries on the NVRAM card are low (if the filer is a PCI-based system).
With a hot spare disk: If you reserve one or more disks as hot spare disks when you
configure your filer, the filer also enters degraded mode after a disk failure. However,
the filer immediately begins rebuilding the missing data in the background on the hot
spare disk, with minimal interruption to file service.
The filer logs this activity in the /etc/messages file and does not automatically shut
down. If you turn off the filer while it is in degraded mode, it stops data reconstruc-
tion. After you turn the filer back on, the filer restarts the data reconstruction process
from the beginning.
Except for a loss in performance while data is rebuilt on the hot spare disk, the failure
of a single disk is transparent to the user. The filer exits degraded mode and returns to
normal operation after it finishes reconstructing the data.
Dell recommends that you replace the failed disk with a new hot spare disk after the
filer finishes reconstructing data. This way, the filer continues to have a hot spare disk
that it can use in case another disk fails.