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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 November 18, 2024 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 Ns Fl e | Ns Fl p | Fl s Ns | Fl C Ns 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 65When scrubbing a pool with encrypted filesystems the keys do not need to be 66loaded. 67However, if the keys are not loaded and an unrepairable checksum error is 68detected the file name cannot be included in the 69.Nm zpool Cm status Fl v 70verbose error report. 71.Pp 72Because scrubbing and resilvering are I/O-intensive operations, ZFS only allows 73one at a time. 74.Pp 75A scrub is split into two parts: metadata scanning and block scrubbing. 76The metadata scanning sorts blocks into large sequential ranges which can then 77be read much more efficiently from disk when issuing the scrub I/O. 78.Pp 79If a scrub is paused, the 80.Nm zpool Cm scrub 81resumes it. 82If a resilver is in progress, ZFS does not allow a scrub to be started until the 83resilver completes. 84.Pp 85Note that, due to changes in pool data on a live system, it is possible for 86scrubs to progress slightly beyond 100% completion. 87During this period, no completion time estimate will be provided. 88. 89.Sh OPTIONS 90.Bl -tag -width "-s" 91.It Fl s 92Stop scrubbing. 93.It Fl p 94Pause scrubbing. 95Scrub pause state and progress are periodically synced to disk. 96If the system is restarted or pool is exported during a paused scrub, 97even after import, scrub will remain paused until it is resumed. 98Once resumed the scrub will pick up from the place where it was last 99checkpointed to disk. 100To resume a paused scrub issue 101.Nm zpool Cm scrub 102or 103.Nm zpool Cm scrub 104.Fl e 105again. 106.It Fl w 107Wait until scrub has completed before returning. 108.It Fl e 109Only scrub files with known data errors as reported by 110.Nm zpool Cm status Fl v . 111The pool must have been scrubbed at least once with the 112.Sy head_errlog 113feature enabled to use this option. 114Error scrubbing cannot be run simultaneously with regular scrubbing or 115resilvering, nor can it be run when a regular scrub is paused. 116.It Fl C 117Continue scrub from last saved txg (see zpool 118.Sy last_scrubbed_txg 119property). 120.El 121.Sh EXAMPLES 122.Ss Example 1 123Status of pool with ongoing scrub: 124.sp 125.Bd -literal -compact 126.No # Nm zpool Cm status 127 ... 128 scan: scrub in progress since Sun Jul 25 16:07:49 2021 129 403M / 405M scanned at 100M/s, 68.4M / 405M issued at 10.0M/s 130 0B repaired, 16.91% done, 00:00:04 to go 131 ... 132.Ed 133.Pp 134Where metadata which references 403M of file data has been 135scanned at 100M/s, and 68.4M of that file data has been 136scrubbed sequentially at 10.0M/s. 137.Sh PERIODIC SCRUB 138On machines using systemd, scrub timers can be enabled on per-pool basis. 139.Nm weekly 140and 141.Nm monthly 142timer units are provided. 143.Bl -tag -width Ds 144.It Xo 145.Xc 146.Nm systemctl 147.Cm enable 148.Cm zfs-scrub-\fIweekly\fB@\fIrpool\fB.timer 149.Cm --now 150.It Xo 151.Xc 152.Nm systemctl 153.Cm enable 154.Cm zfs-scrub-\fImonthly\fB@\fIotherpool\fB.timer 155.Cm --now 156.El 157. 158.Sh SEE ALSO 159.Xr systemd.timer 5 , 160.Xr zpool-iostat 8 , 161.Xr zpool-resilver 8 , 162.Xr zpool-status 8 163