I'm compressing a dd img of a 3TB drive onto a zvol in ZFS for Linux. I enabled compression (lz4) and let it transfer. The pool just consists of one 3TB drive (for now). I am expecting to have 86Gigs more in zfs list than I appear to. Here are some figures:
$ zfs --version
zfs-0.8.3-1ubuntu12
zfs-kmod-0.8.3-1ubuntu12
$ zfs list
NAME USED AVAIL REFER MOUNTPOINT
tank 2.46T 176G 96K /tank
tank/justin 100K 176G 100K /tank/justin
tank/seagate_3tb_01_20_2020 2.46T 176G 2.46T -
$ zpool list
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
tank 2.72T 2.46T 263G - - 0% 90% 1.00x ONLINE -
$ zfs get all tank/seagate_3tb_01_20_2020
NAME PROPERTY VALUE SOURCE
tank/seagate_3tb_01_20_2020 type volume -
tank/seagate_3tb_01_20_2020 creation Mon Apr 27 0:26 2020 -
tank/seagate_3tb_01_20_2020 used 2.46T -
tank/seagate_3tb_01_20_2020 available 176G -
tank/seagate_3tb_01_20_2020 referenced 2.46T -
tank/seagate_3tb_01_20_2020 compressratio 1.08x -
tank/seagate_3tb_01_20_2020 reservation none default
tank/seagate_3tb_01_20_2020 volsize 3T local
tank/seagate_3tb_01_20_2020 volblocksize 8K default
tank/seagate_3tb_01_20_2020 checksum on default
tank/seagate_3tb_01_20_2020 compression lz4 local
tank/seagate_3tb_01_20_2020 readonly off default
tank/seagate_3tb_01_20_2020 createtxg 10771 -
tank/seagate_3tb_01_20_2020 copies 1 default
tank/seagate_3tb_01_20_2020 refreservation none local
tank/seagate_3tb_01_20_2020 guid 17633099490469485439 -
tank/seagate_3tb_01_20_2020 primarycache all default
tank/seagate_3tb_01_20_2020 secondarycache all default
tank/seagate_3tb_01_20_2020 usedbysnapshots 0B -
tank/seagate_3tb_01_20_2020 usedbydataset 2.46T -
tank/seagate_3tb_01_20_2020 usedbychildren 0B -
tank/seagate_3tb_01_20_2020 usedbyrefreservation 0B -
tank/seagate_3tb_01_20_2020 logbias latency default
tank/seagate_3tb_01_20_2020 objsetid 906 -
tank/seagate_3tb_01_20_2020 dedup off default
tank/seagate_3tb_01_20_2020 mlslabel none default
tank/seagate_3tb_01_20_2020 sync standard default
tank/seagate_3tb_01_20_2020 refcompressratio 1.08x -
tank/seagate_3tb_01_20_2020 written 2.46T -
tank/seagate_3tb_01_20_2020 logicalused 2.65T -
tank/seagate_3tb_01_20_2020 logicalreferenced 2.65T -
tank/seagate_3tb_01_20_2020 volmode default default
tank/seagate_3tb_01_20_2020 snapshot_limit none default
tank/seagate_3tb_01_20_2020 snapshot_count none default
tank/seagate_3tb_01_20_2020 snapdev hidden default
tank/seagate_3tb_01_20_2020 context none default
tank/seagate_3tb_01_20_2020 fscontext none default
tank/seagate_3tb_01_20_2020 defcontext none default
tank/seagate_3tb_01_20_2020 rootcontext none default
tank/seagate_3tb_01_20_2020 redundant_metadata all default
tank/seagate_3tb_01_20_2020 encryption off default
tank/seagate_3tb_01_20_2020 keylocation none default
tank/seagate_3tb_01_20_2020 keyformat none default
tank/seagate_3tb_01_20_2020 pbkdf2iters 0 default
I have no snapshots, have disabled reservation and refreservasion, but still have some sort of space discrepancy between the zpool and list.(Yes, I've read the articles, I know they won't be the same, but this is a single disk in the pool, surely ~86G is too much).It seems that I'm not regaining my compression savings to reuse elsewhere (I can only use 176G instead of 263G)
I'm hoping it's a config change I'm missing.
EDIT (zpool get all tank, created with just zpool create tank /dev/sda)
$ zpool get all tank
NAME PROPERTY VALUE SOURCE
tank size 2.72T -
tank capacity 90% -
tank altroot - default
tank health ONLINE -
tank guid 901113366047988914 -
tank version - default
tank bootfs - default
tank delegation on default
tank autoreplace off default
tank cachefile - default
tank failmode wait default
tank listsnapshots on local
tank autoexpand off default
tank dedupditto 0 default
tank dedupratio 1.00x -
tank free 263G -
tank allocated 2.46T -
tank readonly off -
tank ashift 0 default
tank comment - default
tank expandsize - -
tank freeing 0 -
tank fragmentation 0% -
tank leaked 0 -
tank multihost off default
tank checkpoint - -
tank load_guid 9196014585464561985 -
tank autotrim off default
tank feature@async_destroy enabled local
tank feature@empty_bpobj active local
tank feature@lz4_compress active local
tank feature@multi_vdev_crash_dump enabled local
tank feature@spacemap_histogram active local
tank feature@enabled_txg active local
tank feature@hole_birth active local
tank feature@extensible_dataset active local
tank feature@embedded_data active local
tank feature@bookmarks enabled local
tank feature@filesystem_limits enabled local
tank feature@large_blocks enabled local
tank feature@large_dnode enabled local
tank feature@sha512 enabled local
tank feature@skein enabled local
tank feature@edonr enabled local
tank feature@userobj_accounting active local
tank feature@encryption enabled local
tank feature@project_quota active local
tank feature@device_removal enabled local
tank feature@obsolete_counts enabled local
tank feature@zpool_checkpoint enabled local
tank feature@spacemap_v2 active local
tank feature@allocation_classes enabled local
tank feature@resilver_defer enabled local
tank feature@bookmark_v2 enabled local
I asked this exact question on the openzfs github and got my answer:
https://github.com/openzfs/zfs/issues/10260#issuecomment-620332829
TLDR: Look at your spa_slop_shift setting.