man/man8/zdb.8

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  12 .\" Copyright 2012, Richard Lowe.
  13 .\" Copyright (c) 2012, 2017 by Delphix. All rights reserved.
  14 .\" Copyright 2017 Nexenta Systems, Inc.
  15 .\" Copyright (c) 2017 Lawrence Livermore National Security, LLC.
  16 .\" Copyright (c) 2017 Intel Corporation.
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  18 .Dd April 14, 2017
  19 .Dt ZDB 8 SMM
  20 .Os Linux
  21 .Sh NAME
  22 .Nm zdb
  23 .Nd display zpool debugging and consistency information
  24 .Sh SYNOPSIS
  25 .Nm
  26 .Op Fl AbcdDFGhiLMPsvX
  27 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
  28 .Op Fl I Ar inflight I/Os
  29 .Oo Fl o Ar var Ns = Ns Ar value Oc Ns ...
  30 .Op Fl t Ar txg
  31 .Op Fl U Ar cache
  32 .Op Fl x Ar dumpdir
  33 .Op Ar poolname Op Ar object ...
  34 .Nm
  35 .Op Fl AdiPv
  36 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
  37 .Op Fl U Ar cache
  38 .Ar dataset Op Ar object ...
  39 .Nm
  40 .Fl C
  41 .Op Fl A
  42 .Op Fl U Ar cache
  43 .Nm
  44 .Fl E
  45 .Op Fl A
  46 .Ar word0 Ns : Ns Ar word1 Ns :...: Ns Ar word15
  47 .Nm
  48 .Fl l
  49 .Op Fl Aqu
  50 .Ar device
  51 .Nm
  52 .Fl m
  53 .Op Fl AFLPX
  54 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
  55 .Op Fl t Ar txg
  56 .Op Fl U Ar cache
  57 .Ar poolname Op Ar vdev Op Ar metaslab ...
  58 .Nm
  59 .Fl O
  60 .Ar dataset path
  61 .Nm
  62 .Fl R
  63 .Op Fl A
  64 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
  65 .Op Fl U Ar cache
  66 .Ar poolname vdev Ns : Ns Ar offset Ns : Ns Ar size Ns Op : Ns Ar flags
  67 .Nm
  68 .Fl S
  69 .Op Fl AP
  70 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
  71 .Op Fl U Ar cache
  72 .Ar poolname
  73 .Sh DESCRIPTION
  74 The
  75 .Nm
  76 utility displays information about a ZFS pool useful for debugging and performs
  77 some amount of consistency checking.
  78 It is a not a general purpose tool and options
  79 .Pq and facilities
  80 may change.
  81 This is neither a
  82 .Xr fsck 1M
  83 nor an
  84 .Xr fsdb 1M
  85 utility.
  86 .Pp
  87 The output of this command in general reflects the on-disk structure of a ZFS
  88 pool, and is inherently unstable.
  89 The precise output of most invocations is not documented, a knowledge of ZFS
  90 internals is assumed.
  91 .Pp
  92 If the
  93 .Ar dataset
  94 argument does not contain any
  95 .Qq Sy /
  96 or
  97 .Qq Sy @
  98 characters, it is interpreted as a pool name.
  99 The root dataset can be specified as
 100 .Ar pool Ns /
 101 .Pq pool name followed by a slash .
 102 .Pp
 103 When operating on an imported and active pool it is possible, though unlikely,
 104 that zdb may interpret inconsistent pool data and behave erratically.
 105 .Sh OPTIONS
 106 Display options:
 107 .Bl -tag -width Ds
 108 .It Fl b
 109 Display statistics regarding the number, size
 110 .Pq logical, physical and allocated
 111 and deduplication of blocks.
 112 .It Fl c
 113 Verify the checksum of all metadata blocks while printing block statistics
 114 .Po see
 115 .Fl b
 116 .Pc .
 117 .Pp
 118 If specified multiple times, verify the checksums of all blocks.
 119 .It Fl C
 120 Display information about the configuration.
 121 If specified with no other options, instead display information about the cache
 122 file
 123 .Pq Pa /etc/zfs/zpool.cache .
 124 To specify the cache file to display, see
 125 .Fl U .
 126 .Pp
 127 If specified multiple times, and a pool name is also specified display both the
 128 cached configuration and the on-disk configuration.
 129 If specified multiple times with
 130 .Fl e
 131 also display the configuration that would be used were the pool to be imported.
 132 .It Fl d
 133 Display information about datasets.
 134 Specified once, displays basic dataset information: ID, create transaction,
 135 size, and object count.
 136 .Pp
 137 If specified multiple times provides greater and greater verbosity.
 138 .Pp
 139 If object IDs are specified, display information about those specific objects
 140 only.
 141 .It Fl D
 142 Display deduplication statistics, including the deduplication ratio
 143 .Pq Sy dedup ,
 144 compression ratio
 145 .Pq Sy compress ,
 146 inflation due to the zfs copies property
 147 .Pq Sy copies ,
 148 and an overall effective ratio
 149 .Pq Sy dedup No * Sy compress No / Sy copies .
 150 .It Fl DD
 151 Display a histogram of deduplication statistics, showing the allocated
 152 .Pq physically present on disk
 153 and referenced
 154 .Pq logically referenced in the pool
 155 block counts and sizes by reference count.
 156 .It Fl DDD
 157 Display the statistics independently for each deduplication table.
 158 .It Fl DDDD
 159 Dump the contents of the deduplication tables describing duplicate blocks.
 160 .It Fl DDDDD
 161 Also dump the contents of the deduplication tables describing unique blocks.
 162 .It Fl E Ar word0 Ns : Ns Ar word1 Ns :...: Ns Ar word15
 163 Decode and display block from an embedded block pointer specified by the
 164 .Ar word
 165 arguments.
 166 .It Fl h
 167 Display pool history similar to
 168 .Nm zpool Cm history ,
 169 but include internal changes, transaction, and dataset information.
 170 .It Fl i
 171 Display information about intent log
 172 .Pq ZIL
 173 entries relating to each dataset.
 174 If specified multiple times, display counts of each intent log transaction type.
 175 .It Fl l Ar device
 176 Read the vdev labels from the specified device.
 177 .Nm Fl l
 178 will return 0 if valid label was found, 1 if error occurred, and 2 if no valid
 179 labels were found. Each unique configuration is displayed only once.
 180 .It Fl ll Ar device
 181 In addition display label space usage stats.
 182 .It Fl lll Ar device
 183 Display every configuration, unique or not.
 184 .Pp
 185 If the
 186 .Fl q
 187 option is also specified, don't print the labels.
 188 .Pp
 189 If the
 190 .Fl u
 191 option is also specified, also display the uberblocks on this device.  Specify
 192 multiple times to increase verbosity.
 193 .It Fl L
 194 Disable leak tracing and the loading of space maps.
 195 By default,
 196 .Nm
 197 verifies that all non-free blocks are referenced, which can be very expensive.
 198 .It Fl m
 199 Display the offset, spacemap, and free space of each metaslab.
 200 .It Fl mm
 201 Also display information about the on-disk free space histogram associated with
 202 each metaslab.
 203 .It Fl mmm
 204 Display the maximum contiguous free space, the in-core free space histogram, and
 205 the percentage of free space in each space map.
 206 .It Fl mmmm
 207 Display every spacemap record.
 208 .It Fl M
 209 Display the offset, spacemap, and free space of each metaslab.
 210 .It Fl MM
 211 Also display information about the maximum contiguous free space and the
 212 percentage of free space in each space map.
 213 .It Fl MMM
 214 Display every spacemap record.
 215 .It Fl O Ar dataset path
 216 Look up the specified
 217 .Ar path
 218 inside of the
 219 .Ar dataset
 220 and display its metadata and indirect blocks.
 221 Specified
 222 .Ar path
 223 must be relative to the root of
 224 .Ar dataset .
 225 This option can be combined with
 226 .Fl v
 227 for increasing verbosity.
 228 .It Fl R Ar poolname vdev Ns : Ns Ar offset Ns : Ns Ar size Ns Op : Ns Ar flags
 229 Read and display a block from the specified device.
 230 By default the block is displayed as a hex dump, but see the description of the
 231 .Sy r
 232 flag, below.
 233 .Pp
 234 The block is specified in terms of a colon-separated tuple
 235 .Ar vdev
 236 .Pq an integer vdev identifier
 237 .Ar offset
 238 .Pq the offset within the vdev
 239 .Ar size
 240 .Pq the size of the block to read
 241 and, optionally,
 242 .Ar flags
 243 .Pq a set of flags, described below .
 244 .Pp
 245 .Bl -tag -compact -width "b offset"
 246 .It Sy b Ar offset
 247 Print block pointer
 248 .It Sy d
 249 Decompress the block
 250 .It Sy e
 251 Byte swap the block
 252 .It Sy g
 253 Dump gang block header
 254 .It Sy i
 255 Dump indirect block
 256 .It Sy r
 257 Dump raw uninterpreted block data
 258 .El
 259 .It Fl s
 260 Report statistics on
 261 .Nm zdb
 262 I/O.
 263 Display operation counts, bandwidth, and error counts of I/O to the pool from
 264 .Nm .
 265 .It Fl S
 266 Simulate the effects of deduplication, constructing a DDT and then display
 267 that DDT as with
 268 .Fl DD .
 269 .It Fl u
 270 Display the current uberblock.
 271 .El
 272 .Pp
 273 Other options:
 274 .Bl -tag -width Ds
 275 .It Fl A
 276 Do not abort should any assertion fail.
 277 .It Fl AA
 278 Enable panic recovery, certain errors which would otherwise be fatal are
 279 demoted to warnings.
 280 .It Fl AAA
 281 Do not abort if asserts fail and also enable panic recovery.
 282 .It Fl e Op Fl p Ar path ...
 283 Operate on an exported pool, not present in
 284 .Pa /etc/zfs/zpool.cache .
 285 The
 286 .Fl p
 287 flag specifies the path under which devices are to be searched.
 288 .It Fl x Ar dumpdir
 289 All blocks accessed will be copied to files in the specified directory.
 290 The blocks will be placed in sparse files whose name is the same as
 291 that of the file or device read.
 292 .Nm
 293 can be then run on the generated files.
 294 Note that the
 295 .Fl bbc
 296 flags are sufficient to access
 297 .Pq and thus copy
 298 all metadata on the pool.
 299 .It Fl F
 300 Attempt to make an unreadable pool readable by trying progressively older
 301 transactions.
 302 .It Fl G
 303 Dump the contents of the zfs_dbgmsg buffer before exiting
 304 .Nm .
 305 zfs_dbgmsg is a buffer used by ZFS to dump advanced debug information.
 306 .It Fl I Ar inflight I/Os
 307 Limit the number of outstanding checksum I/Os to the specified value.
 308 The default value is 200.
 309 This option affects the performance of the
 310 .Fl c
 311 option.
 312 .It Fl o Ar var Ns = Ns Ar value ...
 313 Set the given global libzpool variable to the provided value.
 314 The value must be an unsigned 32-bit integer.
 315 Currently only little-endian systems are supported to avoid accidentally setting
 316 the high 32 bits of 64-bit variables.
 317 .It Fl P
 318 Print numbers in an unscaled form more amenable to parsing, eg. 1000000 rather
 319 than 1M.
 320 .It Fl t Ar transaction
 321 Specify the highest transaction to use when searching for uberblocks.
 322 See also the
 323 .Fl u
 324 and
 325 .Fl l
 326 options for a means to see the available uberblocks and their associated
 327 transaction numbers.
 328 .It Fl U Ar cachefile
 329 Use a cache file other than
 330 .Pa /etc/zfs/zpool.cache .
 331 .It Fl v
 332 Enable verbosity.
 333 Specify multiple times for increased verbosity.
 334 .It Fl V
 335 Attempt verbatim import.
 336 This mimics the behavior of the kernel when loading a pool from a cachefile.
 337 Only usable with
 338 .Fl e .
 339 .It Fl X
 340 Attempt
 341 .Qq extreme
 342 transaction rewind, that is attempt the same recovery as
 343 .Fl F
 344 but read transactions otherwise deemed too old.
 345 .El
 346 .Pp
 347 Specifying a display option more than once enables verbosity for only that
 348 option, with more occurrences enabling more verbosity.
 349 .Pp
 350 If no options are specified, all information about the named pool will be
 351 displayed at default verbosity.
 352 .Sh EXAMPLES
 353 .Bl -tag -width Ds
 354 .It Xo
 355 .Sy Example 1
 356 Display the configuration of imported pool
 357 .Pa rpool
 358 .Xc
 359 .Bd -literal
 360 # zdb -C rpool
 361
 362 MOS Configuration:
 363         version: 28
 364         name: 'rpool'
 365  ...
 366 .Ed
 367 .It Xo
 368 .Sy Example 2
 369 Display basic dataset information about
 370 .Pa rpool
 371 .Xc
 372 .Bd -literal
 373 # zdb -d rpool
 374 Dataset mos [META], ID 0, cr_txg 4, 26.9M, 1051 objects
 375 Dataset rpool/swap [ZVOL], ID 59, cr_txg 356, 486M, 2 objects
 376  ...
 377 .Ed
 378 .It Xo
 379 .Sy Example 3
 380 Display basic information about object 0 in
 381 .Pa rpool/export/home
 382 .Xc
 383 .Bd -literal
 384 # zdb -d rpool/export/home 0
 385 Dataset rpool/export/home [ZPL], ID 137, cr_txg 1546, 32K, 8 objects
 386
 387     Object  lvl   iblk   dblk  dsize  lsize   %full  type
 388          0    7    16K    16K  15.0K    16K   25.00  DMU dnode
 389 .Ed
 390 .It Xo
 391 .Sy Example 4
 392 Display the predicted effect of enabling deduplication on
 393 .Pa rpool
 394 .Xc
 395 .Bd -literal
 396 # zdb -S rpool
 397 Simulated DDT histogram:
 398
 399 bucket              allocated                       referenced
 400 ______   ______________________________   ______________________________
 401 refcnt   blocks   LSIZE   PSIZE   DSIZE   blocks   LSIZE   PSIZE   DSIZE
 402 ------   ------   -----   -----   -----   ------   -----   -----   -----
 403      1     694K   27.1G   15.0G   15.0G     694K   27.1G   15.0G   15.0G
 404      2    35.0K   1.33G    699M    699M    74.7K   2.79G   1.45G   1.45G
 405  ...
 406 dedup = 1.11, compress = 1.80, copies = 1.00, dedup * compress / copies = 2.00
 407 .Ed
 408 .El
 409 .Sh SEE ALSO
 410 .Xr zfs 8 ,
 411 .Xr zpool 8