Suggestion: Better sVDEV Planning, Oversight Tools in GUI

@etorix

I was able to run the command and here’s the output:

Traversing all blocks ...

39.2T completed (47718MB/s) estimated time remaining: 0hr 00min 00sec
        bp count:             273931836
        ganged count:                 0
        bp logical:      35487125886976      avg: 129547
        bp physical:     34389847032320      avg: 125541     compression:   1.03
        bp allocated:    43050878574592      avg: 157159     compression:   0.82
        bp deduped:                   0    ref>1:      0   deduplication:   1.00
        Normal class:    43050878550016     used: 53.83%
        Embedded log class          16384     used:  0.00%

        additional, non-pointer bps of type 0:    1518161
         number of (compressed) bytes:  number of bps
                         17:   3318 *
                         18:   1384 *
                         19:     27 *
                         20:    207 *
                         21:    198 *
                         22:   1248 *
                         23:     61 *
                         24:    979 *
                         25:    138 *
                         26:     76 *
                         27: 675340 ****************************************
                         28:   3692 *
                         29:   9781 *
                         30:  12176 *
                         31:    141 *
                         32:   1530 *
                         33:   2856 *
                         34:     36 *
                         35:   1987 *
                         36:     57 *
                         37:    154 *
                         38:   9987 *
                         39:    129 *
                         40:    202 *
                         41:    187 *
                         42:   6260 *
                         43:    496 *
                         44:    123 *
                         45:    775 *
                         46:   2391 *
                         47:   1589 *
                         48:    152 *
                         49:   2152 *
                         50:    378 *
                         51:   1461 *
                         52:   4338 *
                         53:   8078 *
                         54:   2054 *
                         55:   4982 *
                         56:   5788 *
                         57:   1405 *
                         58:   2373 *
                         59:   1287 *
                         60:    838 *
                         61:    766 *
                         62:   2011 *
                         63:   1026 *
                         64:   1960 *
                         65:   1670 *
                         66:   2727 *
                         67:   2925 *
                         68:   1467 *
                         69:    866 *
                         70:   1243 *
                         71:   1570 *
                         72:   5891 *
                         73:    743 *
                         74:    678 *
                         75:    904 *
                         76:    881 *
                         77:    945 *
                         78:   1228 *
                         79:   1046 *
                         80:    938 *
                         81:   3387 *
                         82:  30191 **
                         83:  15531 *
                         84:  80625 *****
                         85: 527640 ********************************
                         86:   3008 *
                         87:   1021 *
                         88:   2146 *
                         89:   1445 *
                         90:   1752 *
                         91:   1777 *
                         92:   2815 *
                         93:   3311 *
                         94:   1291 *
                         95:   1051 *
                         96:   1586 *
                         97:   1217 *
                         98:   1082 *
                         99:    865 *
                        100:    785 *
                        101:    694 *
                        102:    628 *
                        103:    843 *
                        104:    989 *
                        105:   1668 *
                        106:   1095 *
                        107:   3665 *
                        108:  13567 *
                        109:   3777 *
                        110:   1231 *
                        111:   1423 *
                        112:   1759 *
        Dittoed blocks on same vdev: 1512665

Blocks  LSIZE   PSIZE   ASIZE     avg    comp   %Total  Type
     -      -       -       -       -       -        -  unallocated
     2    32K      8K     48K     24K    4.00     0.00  object directory
     1    32K      8K     48K     48K    4.00     0.00      L1 object array
    73  36.5K   36.5K   1.71M     24K    1.00     0.00      L0 object array
    74  68.5K   44.5K   1.76M   24.3K    1.54     0.00  object array
     2    32K      4K     24K     12K    8.00     0.00  packed nvlist
     -      -       -       -       -       -        -  packed nvlist size
    93  11.6M    372K   2.18M     24K   32.00     0.00  bpobj
     -      -       -       -       -       -        -  bpobj header
     -      -       -       -       -       -        -  SPA space map header
    73  1.14M    292K   1.71M     24K    4.00     0.00      L1 SPA space map
 4.68K   597M   40.1M    197M   42.1K   14.88     0.00      L0 SPA space map
 4.75K   598M   40.4M    199M   41.8K   14.80     0.00  SPA space map
     6   336K    336K    432K     72K    1.00     0.00  ZIL intent log
    96    12M    384K   1.50M     16K   32.00     0.00      L5 DMU dnode
    96    12M    384K   1.50M     16K   32.00     0.00      L4 DMU dnode
    96    12M    384K   1.50M     16K   32.00     0.00      L3 DMU dnode
    96    12M    388K   1.52M   16.2K   31.67     0.00      L2 DMU dnode
   198  24.8M   4.77M   13.4M   69.3K    5.19     0.00      L1 DMU dnode
 93.9K  1.47G    377M   1.48G   16.1K    3.98     0.00      L0 DMU dnode
 94.4K  1.54G    383M   1.50G   16.2K    4.11     0.00  DMU dnode
    97   388K    388K   1.52M   16.1K    1.00     0.00  DMU objset
     -      -       -       -       -       -        -  DSL directory
    13  6.50K      1K     48K   3.69K    6.50     0.00  DSL directory child map
    11  10.5K      4K     24K   2.18K    2.62     0.00  DSL dataset snap map
    23   322K     80K    480K   20.9K    4.02     0.00  DSL props
     -      -       -       -       -       -        -  DSL dataset
     -      -       -       -       -       -        -  ZFS znode
     -      -       -       -       -       -        -  ZFS V0 ACL
   334  10.4M   1.31M   5.25M   16.1K    7.95     0.00      L3 ZFS plain file
 31.0K   993M    137M    529M   17.0K    7.26     0.00      L2 ZFS plain file
 1.22M  39.0G   12.8G   35.6G   29.2K    3.03     0.09      L1 ZFS plain file
  259M  32.2T   31.3T   39.1T    155K    1.03    99.90      L0 ZFS plain file
  260M  32.3T   31.3T   39.2T    154K    1.03    99.99  ZFS plain file
 12.3K   392M   49.0M    196M     16K    8.00     0.00      L1 ZFS directory
  822K   837M    160M   1.32G   1.64K    5.22     0.00      L0 ZFS directory
  834K  1.20G    209M   1.51G   1.85K    5.87     0.00  ZFS directory
    10    10K     10K    160K     16K    1.00     0.00  ZFS master node
     -      -       -       -       -       -        -  ZFS delete queue
     -      -       -       -       -       -        -  zvol object
     -      -       -       -       -       -        -  zvol prop
     -      -       -       -       -       -        -  other uint8[]
     -      -       -       -       -       -        -  other uint64[]
     -      -       -       -       -       -        -  other ZAP
     -      -       -       -       -       -        -  persistent error log
     1    32K      4K     24K     24K    8.00     0.00      L1 SPA history
     5   640K     40K    216K   43.2K   16.00     0.00      L0 SPA history
     6   672K     44K    240K     40K   15.27     0.00  SPA history
     -      -       -       -       -       -        -  SPA history offsets
     -      -       -       -       -       -        -  Pool properties
     -      -       -       -       -       -        -  DSL permissions
     -      -       -       -       -       -        -  ZFS ACL
     -      -       -       -       -       -        -  ZFS SYSACL
     -      -       -       -       -       -        -  FUID table
     -      -       -       -       -       -        -  FUID table size
     1     1K      1K     24K     24K    1.00     0.00  DSL dataset next clones
     -      -       -       -       -       -        -  scan work queue
   288   144K     512     16K      56   288.00    0.00  ZFS user/group/project used
     -      -       -       -       -       -        -  ZFS user/group/project quota
     -      -       -       -       -       -        -  snapshot refcount tags
     -      -       -       -       -       -        -  DDT ZAP algorithm
     -      -       -       -       -       -        -  DDT statistics
 4.27K  2.20M   2.20M   68.3M     16K    1.00     0.00  System attributes
     -      -       -       -       -       -        -  SA master node
    10    15K     15K    160K     16K    1.00     0.00  SA attr registration
    20   320K     80K    320K     16K    4.00     0.00  SA attr layouts
     -      -       -       -       -       -        -  scan translations
     -      -       -       -       -       -        -  deduplicated block
    98   274K    240K   1.90M   19.8K    1.14     0.00  DSL deadlist map
     -      -       -       -       -       -        -  DSL deadlist map hdr
     1     1K      1K     24K     24K    1.00     0.00  DSL dir clones
     -      -       -       -       -       -        -  bpobj subobj
     -      -       -       -       -       -        -  deferred free
     -      -       -       -       -       -        -  dedup ditto
     2    64K      8K     48K     24K    8.00     0.00      L1 other
   129   537K    101K    648K   5.02K    5.32     0.00      L0 other
   131   601K    109K    696K   5.31K    5.51     0.00  other
    96    12M    384K   1.50M     16K   32.00     0.00      L5 Total
    96    12M    384K   1.50M     16K   32.00     0.00      L4 Total
   430  22.4M   1.69M   6.75M   16.1K   13.30     0.00      L3 Total
 31.1K  1005M    137M    530M   17.0K    7.32     0.00      L2 Total
 1.23M  39.4G   12.9G   35.8G   29.1K    3.05     0.09      L1 Total
  260M  32.2T   31.3T   39.1T    154K    1.03    99.91      L0 Total
  261M  32.3T   31.3T   39.2T    153K    1.03   100.00  Total

Block Size Histogram

  block   psize                lsize                asize
   size   Count   Size   Cum.  Count   Size   Cum.  Count   Size   Cum.
    512:   130K  64.8M  64.8M   130K  64.8M  64.8M      0      0      0
     1K:   117K   148M   213M   117K   148M   213M      0      0      0
     2K:  84.6K   216M   429M  84.6K   216M   429M      0      0      0
     4K:  5.83M  23.4G  23.8G  54.7K   302M   732M      0      0      0
     8K:  2.34M  24.0G  47.8G  59.4K   654M  1.35G  5.72M  45.7G  45.7G
    16K:   431K  8.90G  56.7G   198K  3.74G  5.09G  1.91M  31.7G  77.4G
    32K:   726K  32.7G  89.4G  1.33M  43.6G  48.6G  1.65M  60.0G   137G
    64K:  2.38M   222G   311G  57.6K  5.32G  54.0G  1.65M   161G   298G
   128K:   248M  31.0T  31.3T   258M  32.2T  32.3T   249M  38.9T  39.2T
   256K:      0      0  31.3T      0      0  32.3T    131  40.4M  39.2T
   512K:      0      0  31.3T      0      0  32.3T      0      0  39.2T
     1M:      0      0  3

If i read the guide correctly, it seems like my metadata information on this pool is exactly 35.8GB.

However, i’m bit confused about the Block Size Histogram and need help with the calculation so that i can choose the right capacity for Special VDEV.

Just to give you the insights, this is a 5*RAID-Z1 with Seagate EXOS X16 16TB disks.

Also, any resource or information on what kind of drives to select for the Special VDEV? I’m not sure whether i can use normal consumer grade drives or need Intel Optane (best suited i guess, not really sure tho) and whether it needs to be PLP or not and other features which i’m not aware of. I plan to use 4 way mirror and maybe 250GB disks. Please advice