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download PDF document: zfsd.8.pdf

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 hotspares 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 hotspare.
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 hotspare 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 hotspare will detach automatically.
vdev degrade or fault events If a vdev becomes degraded or faulted, zfsd will activate any available hotspare.
I/O errors 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 hotspare if one is available.
Checksum errors 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 activate a spare anyway.
Spare addition 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), zpool(8)
HISTORY zfsd first appeared in FreeBSD 11.0.
AUTHORS zfsd was originally written by Justin Gibbs <gibbs@FreeBSD.org> and Alan Somers <asomers@FreeBSD.org>
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 14.0-RELEASE-p11 April 18, 2020 FreeBSD 14.0-RELEASE-p11