425 lines
12 KiB
Groff
425 lines
12 KiB
Groff
.\"
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.\" This file and its contents are supplied under the terms of the
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.\" Common Development and Distribution License ("CDDL"), version 1.0.
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.\" You may only use this file in accordance with the terms of version
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.\" 1.0 of the CDDL.
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.\"
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.\" A full copy of the text of the CDDL should have accompanied this
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.\" source. A copy of the CDDL is also available via the Internet at
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.\" http://www.illumos.org/license/CDDL.
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.\"
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.\"
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.\" Copyright 2012, Richard Lowe.
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.\" Copyright (c) 2012, 2018 by Delphix. All rights reserved.
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.\" Copyright 2017 Nexenta Systems, Inc.
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.\" Copyright (c) 2017 Lawrence Livermore National Security, LLC.
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.\" Copyright (c) 2017 Intel Corporation.
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.\"
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.Dd April 14, 2019
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.Dt ZDB 8 SMM
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.Os Linux
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.Sh NAME
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.Nm zdb
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.Nd display zpool debugging and consistency information
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.Sh SYNOPSIS
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.Nm
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.Op Fl AbcdDFGhikLMPsvXY
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.Op Fl e Oo Fl V Oc Op Fl p Ar path ...
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.Op Fl I Ar inflight I/Os
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.Oo Fl o Ar var Ns = Ns Ar value Oc Ns ...
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.Op Fl t Ar txg
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.Op Fl U Ar cache
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.Op Fl x Ar dumpdir
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.Op Ar poolname Op Ar object ...
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.Nm
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.Op Fl AdiPv
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.Op Fl e Oo Fl V Oc Op Fl p Ar path ...
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.Op Fl U Ar cache
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.Ar dataset Op Ar object ...
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.Nm
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.Fl C
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.Op Fl A
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.Op Fl U Ar cache
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.Nm
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.Fl E
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.Op Fl A
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.Ar word0 Ns \&: Ns Ar word1 Ns :...: Ns Ar word15
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.Nm
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.Fl l
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.Op Fl Aqu
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.Ar device
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.Nm
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.Fl m
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.Op Fl AFLPXY
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.Op Fl e Oo Fl V Oc Op Fl p Ar path ...
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.Op Fl t Ar txg
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.Op Fl U Ar cache
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.Ar poolname Op Ar vdev Op Ar metaslab ...
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.Nm
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.Fl O
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.Ar dataset path
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.Nm
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.Fl R
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.Op Fl A
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.Op Fl e Oo Fl V Oc Op Fl p Ar path ...
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.Op Fl U Ar cache
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.Ar poolname vdev Ns \&: Ns Ar offset Ns \&: Ns Ar [<lsize>/]<psize> Ns Op : Ns Ar flags
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.Nm
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.Fl S
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.Op Fl AP
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.Op Fl e Oo Fl V Oc Op Fl p Ar path ...
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.Op Fl U Ar cache
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.Ar poolname
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.Sh DESCRIPTION
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The
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.Nm
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utility displays information about a ZFS pool useful for debugging and performs
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some amount of consistency checking.
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It is a not a general purpose tool and options
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.Pq and facilities
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may change.
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This is not a
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.Xr fsck 8
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utility.
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.Pp
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The output of this command in general reflects the on-disk structure of a ZFS
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pool, and is inherently unstable.
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The precise output of most invocations is not documented, a knowledge of ZFS
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internals is assumed.
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.Pp
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If the
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.Ar dataset
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argument does not contain any
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.Qq Sy /
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or
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.Qq Sy @
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characters, it is interpreted as a pool name.
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The root dataset can be specified as
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.Ar pool Ns /
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.Pq pool name followed by a slash .
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.Pp
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When operating on an imported and active pool it is possible, though unlikely,
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that zdb may interpret inconsistent pool data and behave erratically.
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.Sh OPTIONS
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Display options:
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.Bl -tag -width Ds
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.It Fl b
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Display statistics regarding the number, size
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.Pq logical, physical and allocated
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and deduplication of blocks.
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.It Fl c
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Verify the checksum of all metadata blocks while printing block statistics
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.Po see
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.Fl b
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.Pc .
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.Pp
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If specified multiple times, verify the checksums of all blocks.
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.It Fl C
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Display information about the configuration.
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If specified with no other options, instead display information about the cache
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file
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.Pq Pa /etc/zfs/zpool.cache .
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To specify the cache file to display, see
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.Fl U .
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.Pp
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If specified multiple times, and a pool name is also specified display both the
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cached configuration and the on-disk configuration.
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If specified multiple times with
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.Fl e
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also display the configuration that would be used were the pool to be imported.
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.It Fl d
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Display information about datasets.
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Specified once, displays basic dataset information: ID, create transaction,
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size, and object count.
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.Pp
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If specified multiple times provides greater and greater verbosity.
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.Pp
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If object IDs are specified, display information about those specific objects
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only.
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.It Fl D
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Display deduplication statistics, including the deduplication ratio
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.Pq Sy dedup ,
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compression ratio
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.Pq Sy compress ,
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inflation due to the zfs copies property
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.Pq Sy copies ,
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and an overall effective ratio
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.Pq Sy dedup No * Sy compress No / Sy copies .
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.It Fl DD
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Display a histogram of deduplication statistics, showing the allocated
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.Pq physically present on disk
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and referenced
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.Pq logically referenced in the pool
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block counts and sizes by reference count.
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.It Fl DDD
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Display the statistics independently for each deduplication table.
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.It Fl DDDD
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Dump the contents of the deduplication tables describing duplicate blocks.
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.It Fl DDDDD
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Also dump the contents of the deduplication tables describing unique blocks.
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.It Fl E Ar word0 Ns \&: Ns Ar word1 Ns :...: Ns Ar word15
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Decode and display block from an embedded block pointer specified by the
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.Ar word
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arguments.
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.It Fl h
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Display pool history similar to
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.Nm zpool Cm history ,
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but include internal changes, transaction, and dataset information.
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.It Fl i
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Display information about intent log
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.Pq ZIL
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entries relating to each dataset.
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If specified multiple times, display counts of each intent log transaction type.
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.It Fl k
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Examine the checkpointed state of the pool.
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Note, the on disk format of the pool is not reverted to the checkpointed state.
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.It Fl l Ar device
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Read the vdev labels from the specified device.
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.Nm Fl l
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will return 0 if valid label was found, 1 if error occurred, and 2 if no valid
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labels were found. Each unique configuration is displayed only once.
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.It Fl ll Ar device
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In addition display label space usage stats.
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.It Fl lll Ar device
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Display every configuration, unique or not.
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.Pp
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If the
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.Fl q
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option is also specified, don't print the labels.
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.Pp
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If the
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.Fl u
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option is also specified, also display the uberblocks on this device. Specify
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multiple times to increase verbosity.
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.It Fl L
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Disable leak detection and the loading of space maps.
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By default,
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.Nm
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verifies that all non-free blocks are referenced, which can be very expensive.
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.It Fl m
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Display the offset, spacemap, and free space of each metaslab.
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.It Fl mm
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Also display information about the on-disk free space histogram associated with
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each metaslab.
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.It Fl mmm
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Display the maximum contiguous free space, the in-core free space histogram, and
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the percentage of free space in each space map.
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.It Fl mmmm
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Display every spacemap record.
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.It Fl M
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Display the offset, spacemap, and free space of each metaslab.
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.It Fl MM
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Also display information about the maximum contiguous free space and the
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percentage of free space in each space map.
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.It Fl MMM
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Display every spacemap record.
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.It Fl O Ar dataset path
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Look up the specified
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.Ar path
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inside of the
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.Ar dataset
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and display its metadata and indirect blocks.
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Specified
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.Ar path
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must be relative to the root of
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.Ar dataset .
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This option can be combined with
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.Fl v
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for increasing verbosity.
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.It Xo
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.Fl R Ar poolname vdev Ns \&: Ns Ar offset Ns \&: Ns Ar [<lsize>/]<psize> Ns Op : Ns Ar flags
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.Xc
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Read and display a block from the specified device.
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By default the block is displayed as a hex dump, but see the description of the
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.Sy r
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flag, below.
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.Pp
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The block is specified in terms of a colon-separated tuple
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.Ar vdev
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.Pq an integer vdev identifier
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.Ar offset
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.Pq the offset within the vdev
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.Ar size
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.Pq the physical size, or logical size / physical size
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of the block to read and, optionally,
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.Ar flags
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.Pq a set of flags, described below .
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.Pp
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.Bl -tag -compact -width "b offset"
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.It Sy b Ar offset
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Print block pointer
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.It Sy c
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Calculate and display checksums
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.It Sy d
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Decompress the block. Set environment variable
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.Nm ZDB_NO_ZLE
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to skip zle when guessing.
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.It Sy e
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Byte swap the block
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.It Sy g
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Dump gang block header
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.It Sy i
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Dump indirect block
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.It Sy r
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Dump raw uninterpreted block data
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.It Sy v
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Verbose output for guessing compression algorithm
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.El
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.It Fl s
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Report statistics on
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.Nm zdb
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I/O.
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Display operation counts, bandwidth, and error counts of I/O to the pool from
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.Nm .
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.It Fl S
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Simulate the effects of deduplication, constructing a DDT and then display
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that DDT as with
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.Fl DD .
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.It Fl u
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Display the current uberblock.
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.El
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.Pp
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Other options:
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.Bl -tag -width Ds
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.It Fl A
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Do not abort should any assertion fail.
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.It Fl AA
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Enable panic recovery, certain errors which would otherwise be fatal are
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demoted to warnings.
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.It Fl AAA
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Do not abort if asserts fail and also enable panic recovery.
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.It Fl e Op Fl p Ar path ...
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Operate on an exported pool, not present in
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.Pa /etc/zfs/zpool.cache .
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The
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.Fl p
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flag specifies the path under which devices are to be searched.
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.It Fl x Ar dumpdir
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All blocks accessed will be copied to files in the specified directory.
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The blocks will be placed in sparse files whose name is the same as
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that of the file or device read.
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.Nm
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can be then run on the generated files.
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Note that the
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.Fl bbc
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flags are sufficient to access
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.Pq and thus copy
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all metadata on the pool.
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.It Fl F
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Attempt to make an unreadable pool readable by trying progressively older
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transactions.
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.It Fl G
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Dump the contents of the zfs_dbgmsg buffer before exiting
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.Nm .
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zfs_dbgmsg is a buffer used by ZFS to dump advanced debug information.
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.It Fl I Ar inflight I/Os
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Limit the number of outstanding checksum I/Os to the specified value.
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The default value is 200.
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This option affects the performance of the
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.Fl c
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option.
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.It Fl o Ar var Ns = Ns Ar value ...
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Set the given global libzpool variable to the provided value.
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The value must be an unsigned 32-bit integer.
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Currently only little-endian systems are supported to avoid accidentally setting
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the high 32 bits of 64-bit variables.
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.It Fl P
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Print numbers in an unscaled form more amenable to parsing, eg. 1000000 rather
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than 1M.
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.It Fl t Ar transaction
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Specify the highest transaction to use when searching for uberblocks.
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See also the
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.Fl u
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and
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.Fl l
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options for a means to see the available uberblocks and their associated
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transaction numbers.
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.It Fl U Ar cachefile
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Use a cache file other than
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.Pa /etc/zfs/zpool.cache .
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.It Fl v
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Enable verbosity.
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Specify multiple times for increased verbosity.
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.It Fl V
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Attempt verbatim import.
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This mimics the behavior of the kernel when loading a pool from a cachefile.
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Only usable with
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.Fl e .
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.It Fl X
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Attempt
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.Qq extreme
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transaction rewind, that is attempt the same recovery as
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.Fl F
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but read transactions otherwise deemed too old.
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.It Fl Y
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Attempt all possible combinations when reconstructing indirect split blocks.
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This flag disables the individual I/O deadman timer in order to allow as
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much time as required for the attempted reconstruction.
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.El
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.Pp
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Specifying a display option more than once enables verbosity for only that
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option, with more occurrences enabling more verbosity.
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.Pp
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If no options are specified, all information about the named pool will be
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displayed at default verbosity.
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.Sh EXAMPLES
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.Bl -tag -width Ds
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.It Xo
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.Sy Example 1
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Display the configuration of imported pool
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.Pa rpool
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.Xc
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.Bd -literal
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# zdb -C rpool
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MOS Configuration:
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version: 28
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name: 'rpool'
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...
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.Ed
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.It Xo
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.Sy Example 2
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Display basic dataset information about
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.Pa rpool
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.Xc
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.Bd -literal
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# zdb -d rpool
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Dataset mos [META], ID 0, cr_txg 4, 26.9M, 1051 objects
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Dataset rpool/swap [ZVOL], ID 59, cr_txg 356, 486M, 2 objects
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...
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.Ed
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.It Xo
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.Sy Example 3
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Display basic information about object 0 in
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.Pa rpool/export/home
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.Xc
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.Bd -literal
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# zdb -d rpool/export/home 0
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Dataset rpool/export/home [ZPL], ID 137, cr_txg 1546, 32K, 8 objects
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Object lvl iblk dblk dsize lsize %full type
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0 7 16K 16K 15.0K 16K 25.00 DMU dnode
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.Ed
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.It Xo
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.Sy Example 4
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Display the predicted effect of enabling deduplication on
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.Pa rpool
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.Xc
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.Bd -literal
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# zdb -S rpool
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Simulated DDT histogram:
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bucket allocated referenced
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______ ______________________________ ______________________________
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refcnt blocks LSIZE PSIZE DSIZE blocks LSIZE PSIZE DSIZE
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------ ------ ----- ----- ----- ------ ----- ----- -----
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1 694K 27.1G 15.0G 15.0G 694K 27.1G 15.0G 15.0G
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2 35.0K 1.33G 699M 699M 74.7K 2.79G 1.45G 1.45G
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...
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dedup = 1.11, compress = 1.80, copies = 1.00, dedup * compress / copies = 2.00
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.Ed
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.El
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.Sh SEE ALSO
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.Xr zfs 8 ,
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.Xr zpool 8
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