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657fd33bcf
Functional changes: We implement refcounts of log blocks and their aligned size on the cache device along with two corresponding arcstats. The refcounts are reflected in the header of the device and provide valuable information as to whether log blocks are accounted for correctly. These are dynamically adjusted as log blocks are committed/evicted. zdb also uses this information in the device header and compares it to the corresponding values as reported by dump_l2arc_log_blocks() which emulates l2arc_rebuild(). If the refcounts saved in the device header report higher values, zdb exits with an error. For this feature to work correctly there should be no active writes on the device. This is also employed in the tests of persistent L2ARC. We extend the structure of the cache device header by adding the two new variables mirroring the refcounts after the existing variables to preserve backward compatibility in terms of persistent L2ARC. 1) a new arcstat "l2_log_blk_asize" and refcount "l2ad_lb_asize" which reflect the total aligned size of log blocks on the device. This is also reflected in the header of the cache device as "dh_lb_asize". 2) a new arcstat "l2arc_log_blk_count" and refcount "l2ad_lb_count" which reflect the total number of L2ARC log blocks present on cache devices. It is also reflected in the header of the cache device as "dh_lb_count". In l2arc_rebuild_vdev() if the amount of committed log entries in a log block is 0 and the device header is valid we update the device header. This will facilitate trimming of the whole device in this case when TRIM for L2ARC is implemented. Improve loop protection in l2arc_rebuild() by using the starting offset of the payload of each log block instead of the starting offset of the log block. If the zio in l2arc_write_buffers() fails, restore the lbps array in the header of the device to its previous state in l2arc_write_done(). If l2arc_rebuild() ends the rebuild process without restoring any L2ARC log blocks in ARC and without any other error, this means that the lbps array in the header is pointing to non-existent or invalid log blocks. Reset the device header in this case. In l2arc_rebuild() change the zfs_dbgmsg messages to spa_history_log_internal() making them user visible with zpool history command. Non-functional changes: Make the first test in persistent L2ARC use `zdb -lll` to increase coverage in `zdb.c`. Rename psize with asize when referring to log blocks, since L2ARC_SET_PSIZE stores the vdev aligned size for log blocks. Also rename dh_log_blk_entries to dh_log_entries to make it clear that it is a mirror of l2ad_log_entries. Added comments for both changes. Fix inaccurate comments for example in l2arc_log_blk_restore(). Add asserts at the end in l2arc_evict() and l2arc_write_buffers(). Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #10228
473 lines
13 KiB
Groff
473 lines
13 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[/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 identfiers 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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.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
|