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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 noti-
     fies 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 proper-
     ties.  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 hots-
	pare.

     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 com-
	pletes,	any active hotspare will detach	automatically.

     vdev degrade or fault events
	If a vdev becomes degraded or faulted, zfsd will activate any avail-
	able 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(4) 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(4) will	still
	use it,	but zfsd will activate a spare anyway.

     Spare addition
	If the system administrator adds a hotspare to a pool that is already
	degraded, zfsd will activate the spare.

     Resilver complete
	zfsd will detach any hotspare 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),	zfs(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	11.2			 May 26, 2016			  FreeBSD 11.2

NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | HISTORY | AUTHORS | TODO

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