xref: /freebsd/cddl/usr.sbin/zfsd/zfsd.8 (revision 4b9d6057)
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26.Dd April 18, 2020
27.Dt ZFSD 8
28.Os
29.Sh NAME
30.Nm zfsd
31.Nd ZFS fault management daemon
32.Sh SYNOPSIS
33.Nm
34.Op Fl d
35.Sh DESCRIPTION
36.Nm
37attempts to resolve ZFS faults that the kernel can't resolve by itself.
38It listens to
39.Xr devctl 4
40events, which are how the kernel notifies userland of events such as I/O
41errors and disk removals.
42.Nm
43attempts to resolve these faults by activating or deactivating hot spares
44and onlining offline vdevs.
45.Pp
46The following options are available:
47.Bl -tag -width indent
48.It Fl d
49Run in the foreground instead of daemonizing.
50.El
51.Pp
52System administrators never interact with
53.Nm
54directly.
55Instead, they control its behavior indirectly through zpool configuration.
56There are two ways to influence
57.Nm :
58assigning hotspares and setting pool properties.
59Currently, only the
60.Em autoreplace
61property has any effect.
62See
63.Xr zpool 8
64for details.
65.Pp
66.Nm
67will attempt to resolve the following types of fault:
68.Bl -tag -width a
69.It device removal
70When a leaf vdev disappears,
71.Nm
72will activate any available hotspare.
73.It device arrival
74When a new GEOM device appears,
75.Nm
76will attempt to read its ZFS label, if any.
77If it matches a previously removed vdev on an active pool,
78.Nm
79will online it.
80Once resilvering completes, any active hotspare will detach automatically.
81.Pp
82If the new device has no ZFS label but its physical path matches the
83physical path of a previously removed vdev on an active pool, and that
84pool has the autoreplace property set, then
85.Nm
86will replace the missing vdev with the newly arrived device.
87Once resilvering completes, any active hotspare will detach automatically.
88.It vdev degrade or fault events
89If a vdev becomes degraded or faulted,
90.Nm
91will activate any available hotspare.
92.It I/O errors
93If a leaf vdev generates more than 50 I/O errors in a 60 second period, then
94.Nm
95will mark that vdev as
96.Em FAULTED .
97ZFS will no longer issue any I/Os to it.
98.Nm
99will activate a hotspare if one is available.
100.It Checksum errors
101If a leaf vdev generates more than 50 checksum errors in a 60 second
102period, then
103.Nm
104will mark that vdev as
105.Em DEGRADED .
106ZFS will still use it, but zfsd will activate a spare anyway.
107.It Spare addition
108If the system administrator adds a hotspare to a pool that is already degraded,
109.Nm
110will activate the spare.
111.It Resilver complete
112.Nm
113will detach any hotspare once a permanent replacement finishes resilvering.
114.It Physical path change
115If the physical path of an existing disk changes,
116.Nm
117will attempt to replace any missing disk with the same physical path,
118if its pool's autoreplace property is set.
119.El
120.Pp
121.Nm
122will log interesting events and its actions to syslog with facility
123.Em daemon
124and identity
125.Op zfsd .
126.El
127.Sh FILES
128.Bl -tag -width a -compact
129.It Pa /var/db/zfsd/cases
130When
131.Nm
132exits, it serializes any unresolved casefiles here,
133then reads them back in when next it starts up.
134.El
135.Sh SEE ALSO
136.Xr devctl 4 ,
137.Xr zpool 8
138.Sh HISTORY
139.Nm
140first appeared in
141.Fx 11.0 .
142.Sh AUTHORS
143.Nm
144was originally written by
145.An Justin Gibbs Aq Mt gibbs@FreeBSD.org
146and
147.An Alan Somers Aq Mt asomers@FreeBSD.org
148.Sh TODO
149In the future,
150.Nm
151should be able to resume a pool that became suspended due to device
152removals, if enough missing devices have returned.
153