ZFSD(8) FreeBSD System Manager's Manual ZFSD(8)
NAME
zfsd - ZFS fault management daemon
SYNOPSIS
zfsd [-d]
DESCRIPTION
zfsd attempts to resolve ZFS faults that the kernel can't resolve by
itself. It listens to devctl(4) events, which are how the kernel
notifies userland of events such as I/O errors and disk removals. zfsd
attempts to resolve these faults by activating or deactivating hot spares
and onlining offline vdevs.
The following options are available:
-d Run in the foreground instead of daemonizing.
System administrators never interact with zfsd directly. Instead, they
control its behavior indirectly through zpool configuration. There are
two ways to influence zfsd: assigning hot spares and setting pool
properties. Currently, only the autoreplace property has any effect.
See zpool(8) for details.
zfsd will attempt to resolve the following types of fault:
device removal
When a leaf vdev disappears, zfsd will activate any available hot
spare.
device arrival
When a new GEOM device appears, zfsd will attempt to read its ZFS
label, if any. If it matches a previously removed vdev on an active
pool, zfsd will online it. Once resilvering completes, any active hot
spare will detach automatically.
If the new device has no ZFS label but its physical path matches the
physical path of a previously removed vdev on an active pool, and that
pool has the autoreplace property set, then zfsd will replace the
missing vdev with the newly arrived device. Once resilvering
completes, any active hot spare will detach automatically.
vdev degrade or fault events
If a vdev becomes degraded or faulted, zfsd will activate any
available hot spare.
I/O errors
By default, if a leaf vdev generates more than 50 I/O errors in a 60
second period, then zfsd will mark that vdev as FAULTED. ZFS will no
longer issue any I/Os to it. zfsd will activate a hot spare if one is
available. The defaults can be changed by setting the io_n and/or io_t
vdev properties. See vdevprops(7) for details.
I/O delays
By default, if a leaf vdev generates more than delayed 8 I/O events in
a 60 second period, then zfsd will mark that vdev as FAULTED. ZFS
will no longer issue any I/Os to it. zfsd will activate a hot spare
if one is available. The defaults can be changed by setting the
slow_io_n and/or slow_io_t vdev properties. See vdevprops(7) for
details.
Checksum errors
By default, if a leaf vdev generates more than 50 checksum errors in a
60 second period, then zfsd will mark that vdev as DEGRADED. ZFS will
still use it, but zfsd will also activate a hot spare if one is
available. The defaults can be changed by setting the checksum_n
and/or checksum_t vdev properties. See vdevprops(7) for details.
Spare addition
If the system administrator adds a hot spare to a pool that is already
degraded, zfsd will activate the spare.
Resilver complete
zfsd will detach any hot spare once a permanent replacement finishes
resilvering.
Physical path change
If the physical path of an existing disk changes, zfsd will attempt to
replace any missing disk with the same physical path, if its pool's
autoreplace property is set.
zfsd will log interesting events and its actions to syslog with facility
daemon and identity [zfsd].
FILES
/var/db/zfsd/cases
When zfsd exits, it serializes any unresolved casefiles here, then
reads them back in when next it starts up.
SEE ALSO
devctl(4), vdevprops(7), zpool(8)
HISTORY
zfsd first appeared in FreeBSD 11.0.
AUTHORS
zfsd was originally written by Justin Gibbs <
[email protected]> and
Alan Somers <
[email protected]>
TODO
In the future, zfsd should be able to resume a pool that became suspended
due to device removals, if enough missing devices have returned.
FreeBSD 14.1-RELEASE-p8 February 20, 2024 FreeBSD 14.1-RELEASE-p8