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6774931dfa
Livelists and spacemaps are data structures that are logs of allocations and frees. Livelists entries are block pointers (blkptr_t). Spacemaps entries are ranges of numbers, most often used as to track allocated/freed regions of metaslabs/vdevs. These data structures can become self-inconsistent, for example if a block or range can be "double allocated" (two allocation records without an intervening free) or "double freed" (two free records without an intervening allocation). ZDB (as well as zfs running in the kernel) can detect these inconsistencies when loading livelists and metaslab. However, it generally halts processing when the error is detected. When analyzing an on-disk problem, we often want to know the entire set of inconsistencies, which is not possible with the current behavior. This commit adds a new flag, `zdb -y`, which analyzes the livelist and metaslab data structures and displays all of their inconsistencies. Note that this is different from the leak detection performed by `zdb -b`, which checks for inconsistencies between the spacemaps and the tree of block pointers, but assumes the spacemaps are self-consistent. The specific checks added are: Verify livelists by iterating through each sublivelists and: - report leftover FREEs - report double ALLOCs and double FREEs - record leftover ALLOCs together with their TXG [see Cross Check] Verify spacemaps by iterating over each metaslab and: - iterate over spacemap and then the metaslab's entries in the spacemap log, then report any double FREEs and double ALLOCs Verify that livelists are consistenet with spacemaps. The space referenced by livelists (after using the FREE's to cancel out corresponding ALLOCs) should be allocated, according to the spacemaps. Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Sara Hartse <sara.hartse@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-66031 Closes #10515
479 lines
14 KiB
Groff
479 lines
14 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, 2019 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 AbcdDFGhikLMPsvXYy
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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[/dataset | objset ID]
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.Op Ar object | range ...
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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 poolname[/dataset | objset ID] Op Ar object | range ...
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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 or object ID ranges are specified, display information about
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those specific objects or ranges only.
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.Pp
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An object ID range is specified in terms of a colon-separated tuple of
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the form
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.Ao start Ac Ns : Ns Ao end Ac Ns Op Ns : Ns Ao flags Ac Ns .
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The fields
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.Ar start
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and
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.Ar end
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are integer object identifiers that denote the upper and lower bounds
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of the range. An
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.Ar end
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value of -1 specifies a range with no upper bound. The
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.Ar flags
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field optionally specifies a set of flags, described below, that control
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which object types are dumped. By default, all object types are dumped. A minus
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sign
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.Pq -
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negates the effect of the flag that follows it and has no effect unless
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preceded by the
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.Ar A
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flag. For example, the range 0:-1:A-d will dump all object types except
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for directories.
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.Pp
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.Bl -tag -compact
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.It Sy A
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Dump all objects (this is the default)
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.It Sy d
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Dump ZFS directory objects
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.It Sy f
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Dump ZFS plain file objects
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.It Sy m
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Dump SPA space map objects
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.It Sy z
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Dump ZAP objects
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.It Sy -
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Negate the effect of next flag
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.El
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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 and L2ARC header 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. The presence of L2ARC header is indicated by a specific
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sequence (L2ARC_DEV_HDR_MAGIC). If there is an accounting error in the size
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or the number of L2ARC log blocks
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.Nm Fl l
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will return 1. Each unique configuration is displayed only
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once.
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.It Fl ll Ar device
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In addition display label space usage stats. If a valid L2ARC header was found
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also display the properties of log blocks used for restoring L2ARC contents
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(persistent L2ARC).
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.It Fl lll Ar device
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Display every configuration, unique or not. If a valid L2ARC header was found
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also display the properties of log entries in log blocks used for restoring
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L2ARC contents (persistent L2ARC).
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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 or the L2ARC header.
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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, free space of each metaslab, all the log
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spacemaps and their obsolete entry statistics.
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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 at hex offset
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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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.It Fl y
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Perform validation for livelists that are being deleted.
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Scans through the livelist and metaslabs, checking for duplicate entries
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and compares the two, checking for potential double frees.
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If it encounters issues, warnings will be printed, but the command will not
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necessarily fail.
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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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