ZFS deduplication

• Automatic deduplication and compression of data, selectable per volume or filesystem according to administrator policy

zfs set dedup=on POOL_NAME/FS_NAME

zpool list POOL_NAME

Before activating deduplication:

zpool list ZPOOL_NAME
NAME        SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
ZPOOL_NAME  7.25T   163G  7.09T         -     0%     2%  1.00x  ONLINE  -

zpool get all ZPOOL_NAME | grep dedup
zfs get all | grep dedup

 zpool status -D ZPOOL_NAME 
  pool: ZPOOL_NAME
 state: ONLINE
  scan: none requested
config:

	NAME        STATE     READ WRITE CKSUM
	ZPOOL_NAME    ONLINE       0     0     0
	  sdc       ONLINE       0     0     0

errors: No known data errors

 dedup: DDT entries 259792, size 437B on disk, 141B in core

bucket              allocated                       referenced
______   ______________________________   ______________________________
refcnt   blocks   LSIZE   PSIZE   DSIZE   blocks   LSIZE   PSIZE   DSIZE
------   ------   -----   -----   -----   ------   -----   -----   -----
     1     251K   31.4G   31.4G   31.4G     251K   31.4G   31.4G   31.4G
     4    2.54K    325M    325M    325M    17.8K   2.22G   2.22G   2.22G
 Total     254K   31.7G   31.7G   31.7G     269K   33.6G   33.6G   33.6G

Ref: https://unix.stackexchange.com/questions/438955/zfs-deduplication-does-not-work

See also

• ZFS: ZFS deduplication, ZFS snapshot, zfs list, zpool status, zpool create, zfs create, zfs get all, zfs set, zfs mount, zfs umount, zfs rollback
• deduplication

https://wiki.ubuntu.com/ZFS