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ZFSD(8)			    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 at-
       tempts 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	 prop-
       erties.	 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
	  completes, 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  pe-
	  riod,	 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
	  If the system	administrator adds a hotspare to a pool	 that  is  al-
	  ready	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	facil-
       ity 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  sus-
       pended due to device removals, if enough	missing	devices	have returned.

FreeBSD	13.2			April 18, 2020			       ZFSD(8)

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

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