1.\"
2.\" CDDL HEADER START
3.\"
4.\" The contents of this file are subject to the terms of the
5.\" Common Development and Distribution License (the "License").
6.\" You may not use this file except in compliance with the License.
7.\"
8.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9.\" or http://www.opensolaris.org/os/licensing.
10.\" See the License for the specific language governing permissions
11.\" and limitations under the License.
12.\"
13.\" When distributing Covered Code, include this CDDL HEADER in each
14.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15.\" If applicable, add the following below this CDDL HEADER, with the
16.\" fields enclosed by brackets "[]" replaced with your own identifying
17.\" information: Portions Copyright [yyyy] [name of copyright owner]
18.\"
19.\" CDDL HEADER END
20.\"
21.\" Copyright (c) 2007, Sun Microsystems, Inc. All Rights Reserved.
22.\" Copyright (c) 2012, 2018 by Delphix. All rights reserved.
23.\" Copyright (c) 2012 Cyril Plisko. All Rights Reserved.
24.\" Copyright (c) 2017 Datto Inc.
25.\" Copyright (c) 2018, 2021 George Melikov. All Rights Reserved.
26.\" Copyright 2017 Nexenta Systems, Inc.
27.\" Copyright (c) 2017 Open-E, Inc. All Rights Reserved.
28.\"
29.Dd July 25, 2021
30.Dt ZPOOL-SCRUB 8
31.Os
32.
33.Sh NAME
34.Nm zpool-scrub
35.Nd begin or resume scrub of ZFS storage pools
36.Sh SYNOPSIS
37.Nm zpool
38.Cm scrub
39.Op Fl s Ns | Ns Fl p
40.Op Fl w
41.Ar pool Ns …
42.
43.Sh DESCRIPTION
44Begins a scrub or resumes a paused scrub.
45The scrub examines all data in the specified pools to verify that it checksums
46correctly.
47For replicated
48.Pq mirror, raidz, or draid
49devices, ZFS automatically repairs any damage discovered during the scrub.
50The
51.Nm zpool Cm status
52command reports the progress of the scrub and summarizes the results of the
53scrub upon completion.
54.Pp
55Scrubbing and resilvering are very similar operations.
56The difference is that resilvering only examines data that ZFS knows to be out
57of date
58.Po
59for example, when attaching a new device to a mirror or replacing an existing
60device
61.Pc ,
62whereas scrubbing examines all data to discover silent errors due to hardware
63faults or disk failure.
64.Pp
65Because scrubbing and resilvering are I/O-intensive operations, ZFS only allows
66one at a time.
67.Pp
68A scrub is split into two parts: metadata scanning and block scrubbing.
69The metadata scanning sorts blocks into large sequential ranges which can then
70be read much more efficiently from disk when issuing the scrub I/O.
71.Pp
72If a scrub is paused, the
73.Nm zpool Cm scrub
74resumes it.
75If a resilver is in progress, ZFS does not allow a scrub to be started until the
76resilver completes.
77.Pp
78Note that, due to changes in pool data on a live system, it is possible for
79scrubs to progress slightly beyond 100% completion.
80During this period, no completion time estimate will be provided.
81.
82.Sh OPTIONS
83.Bl -tag -width "-s"
84.It Fl s
85Stop scrubbing.
86.It Fl p
87Pause scrubbing.
88Scrub pause state and progress are periodically synced to disk.
89If the system is restarted or pool is exported during a paused scrub,
90even after import, scrub will remain paused until it is resumed.
91Once resumed the scrub will pick up from the place where it was last
92checkpointed to disk.
93To resume a paused scrub issue
94.Nm zpool Cm scrub
95again.
96.It Fl w
97Wait until scrub has completed before returning.
98.El
99.Sh EXAMPLES
100.Ss Example 1 : No Status of pool with ongoing scrub:
101.Bd -literal -compact
102.No # Nm zpool Cm status
103  ...
104  scan: scrub in progress since Sun Jul 25 16:07:49 2021
105        403M scanned at 100M/s, 68.4M issued at 10.0M/s, 405M total
106        0B repaired, 16.91% done, 00:00:04 to go
107  ...
108.Ed
109.Pp
110Where metadata which references 403M of file data has been
111scanned at 100M/s, and 68.4M of that file data has been
112scrubbed sequentially at 10.0M/s.
113.Sh PERIODIC SCRUB
114On machines using systemd, scrub timers can be enabled on per-pool basis.
115.Nm weekly
116and
117.Nm monthly
118timer units are provided.
119.Bl -tag -width Ds
120.It Xo
121.Xc
122.Nm systemctl
123.Cm enable
124.Cm zfs-scrub-\fIweekly\fB@\fIrpool\fB.timer
125.Cm --now
126.It Xo
127.Xc
128.Nm systemctl
129.Cm enable
130.Cm zfs-scrub-\fImonthly\fB@\fIotherpool\fB.timer
131.Cm --now
132.El
133.
134.Sh SEE ALSO
135.Xr systemd.timer 5 ,
136.Xr zpool-iostat 8 ,
137.Xr zpool-resilver 8 ,
138.Xr zpool-status 8
139