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ZFSD(8)			FreeBSD	System Manager's Manual		       ZFSD(8)

     zfsd -- ZFS fault management daemon

     zfsd [-d]

     zfsd attempts to resolve ZFS faults that the kernel can't resolve by it-
     self.  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 on-
     lining 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-

     device arrival
	When a new GEOM	device appears,	zfsd will attempt to read its ZFS la-
	bel, 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	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 avail-

     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 already
	degraded, zfsd will activate the spare.

     Resilver complete
	zfsd will detach any hotspare once a permanent replacement finishes

     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].

	When zfsd exits, it serializes any unresolved casefiles	here, then
	reads them back	in when	next it	starts up.

     devctl(4),	zpool(8)

     zfsd first	appeared in FreeBSD 11.0.

     zfsd was originally written by Justin Gibbs <> and
     Alan Somers <>

     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	13.0			April 18, 2020			  FreeBSD 13.0


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