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We've heard anecdotes that suggest some confusion/surprise/disappointment that a changed recordsize is not applied during rewrite. Until such time as we actually can do that, we can at least explicitly mention it at something that doesn't work. Sponsored-by: Klara, Inc. Sponsored-by: Wasabi Technology, Inc. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com> Reviewed-by: Allan Jude <allan@klarasystems.com> Signed-off-by: Rob Norris <rob.norris@klarasystems.com> Closes #17898
107 lines
3.2 KiB
Groff
107 lines
3.2 KiB
Groff
.\" SPDX-License-Identifier: CDDL-1.0
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.\"
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.\" CDDL HEADER START
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.\"
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.\" The contents of this file are subject to the terms of the
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.\" Common Development and Distribution License (the "License").
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.\" You may not use this file except in compliance with the License.
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.\"
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.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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.\" or https://opensource.org/licenses/CDDL-1.0.
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.\" See the License for the specific language governing permissions
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.\" and limitations under the License.
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.\"
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.\" When distributing Covered Code, include this CDDL HEADER in each
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.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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.\" If applicable, add the following below this CDDL HEADER, with the
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.\" fields enclosed by brackets "[]" replaced with your own identifying
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.\" information: Portions Copyright [yyyy] [name of copyright owner]
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.\"
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.\" CDDL HEADER END
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.\"
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.\" Copyright (c) 2025 iXsystems, Inc.
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.\" Copyright (c) 2025, Klara, Inc.
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.\"
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.Dd November 5, 2025
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.Dt ZFS-REWRITE 8
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.Os
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.
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.Sh NAME
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.Nm zfs-rewrite
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.Nd rewrite specified files without modification
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.Sh SYNOPSIS
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.Nm zfs
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.Cm rewrite
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.Oo Fl Prvx Ns Oc
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.Op Fl l Ar length
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.Op Fl o Ar offset
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.Ar file Ns | Ns Ar directory Ns …
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.
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.Sh DESCRIPTION
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Rewrite blocks of specified
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.Ar file
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as is without modification at a new location and possibly with new properties,
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as if they were atomically read and written back.
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.No See Sx NOTES .
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for more information about property changes that may be applied during rewrite.
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.Bl -tag -width "-r"
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.It Fl P
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Perform physical rewrite, preserving logical birth time of blocks.
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By default, rewrite updates logical birth times, making blocks appear
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as modified in snapshots and incremental send streams.
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Physical rewrite preserves logical birth times, avoiding unnecessary
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inclusion in incremental streams.
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Physical rewrite requires the
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.Sy physical_rewrite
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feature to be enabled on the pool.
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.It Fl l Ar length
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Rewrite at most this number of bytes.
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.It Fl o Ar offset
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Start at this offset in bytes.
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.It Fl r
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Recurse into directories.
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.It Fl v
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Print names of all successfully rewritten files.
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.It Fl x
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Don't cross file system mount points when recursing.
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.El
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.Sh NOTES
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Rewrite works by replacing an existing block with a new block of the same
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logical size.
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Changed dataset properties that operate on the data or metadata without
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changing the logical size will be applied.
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These include
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.Sy checksum ,
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.Sy compression ,
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.Sy dedup
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and
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.Sy copies .
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Changes to properties that affect the size of a logical block, like
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.Sy recordsize ,
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will have no effect.
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.Pp
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Rewrite of cloned blocks and blocks that are part of any snapshots,
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same as some property changes may increase pool space usage.
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Holes that were never written or were previously zero-compressed are
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not rewritten and will remain holes even if compression is disabled.
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.Pp
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If a
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.Fl l
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or
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.Fl o
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value request a rewrite to regions past the end of the file, then those
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regions are silently ignored, and no error is reported.
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.Pp
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By default, rewritten blocks update their logical birth time,
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meaning they will be included in incremental
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.Nm zfs Cm send
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streams as modified data.
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When the
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.Fl P
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flag is used, rewritten blocks preserve their logical birth time, since
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there are no user data changes.
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.
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.Sh SEE ALSO
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.Xr zfsprops 7 ,
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.Xr zpool-features 7
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