1.\"- 2.\" Copyright (c) 2016 Allan Jude 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.Dd February 20, 2024 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 hot spares 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 hot spare. 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 hot spare 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 hot spare will detach automatically. 88.It vdev degrade or fault events 89If a vdev becomes degraded or faulted, 90.Nm 91will activate any available hot spare. 92.It I/O errors 93By default, if a leaf vdev generates more than 50 I/O errors in a 60 second 94period, then 95.Nm 96will mark that vdev as 97.Em FAULTED . 98ZFS will no longer issue any I/Os to it. 99.Nm 100will activate a hot spare if one is available. The defaults can be changed by 101setting the 102.Em io_n 103and/or 104.Em io_t 105vdev properties. See 106.Xr vdevprops 7 107for details. 108.It I/O delays 109By default, if a leaf vdev generates more than delayed 8 I/O events in a 60 110second period, then 111.Nm 112will mark that vdev as 113.Em FAULTED . 114ZFS will no longer issue any I/Os to it. 115.Nm 116will activate a hot spare if one is available. The defaults can be changed by 117setting the 118.Em slow_io_n 119and/or 120.Em slow_io_t 121vdev properties. See 122.Xr vdevprops 7 123for details. 124.It Checksum errors 125By default, if a leaf vdev generates more than 50 checksum errors in a 60 126second period, then 127.Nm 128will mark that vdev as 129.Em DEGRADED . 130ZFS will still use it, but zfsd will also activate a hot spare if one is 131available. The defaults can be changed by setting the 132.Em checksum_n 133and/or 134.Em checksum_t 135vdev properties. See 136.Xr vdevprops 7 137for details. 138.It Spare addition 139If the system administrator adds a hot spare to a pool that is already degraded, 140.Nm 141will activate the spare. 142.It Resilver complete 143.Nm 144will detach any hot spare once a permanent replacement finishes resilvering. 145.It Physical path change 146If the physical path of an existing disk changes, 147.Nm 148will attempt to replace any missing disk with the same physical path, 149if its pool's autoreplace property is set. 150.El 151.Pp 152.Nm 153will log interesting events and its actions to syslog with facility 154.Em daemon 155and identity 156.Op zfsd . 157.El 158.Sh FILES 159.Bl -tag -width a -compact 160.It Pa /var/db/zfsd/cases 161When 162.Nm 163exits, it serializes any unresolved casefiles here, 164then reads them back in when next it starts up. 165.El 166.Sh SEE ALSO 167.Xr devctl 4 , 168.Xr vdevprops 7 , 169.Xr zpool 8 170.Sh HISTORY 171.Nm 172first appeared in 173.Fx 11.0 . 174.Sh AUTHORS 175.Nm 176was originally written by 177.An Justin Gibbs Aq Mt gibbs@FreeBSD.org 178and 179.An Alan Somers Aq Mt asomers@FreeBSD.org 180.Sh TODO 181In the future, 182.Nm 183should be able to resume a pool that became suspended due to device 184removals, if enough missing devices have returned. 185