dpearcefl
Contributor
- Joined
- Aug 4, 2015
- Messages
- 145
I was asked to compare the storage of certain types of files on a FreeNAS 9.3.1 box and see how much they compressed. I copied about 101 GB of Linux snapshot files into two different volumes, one set to no compression and no dedup and the other volume to LZ4 only.
The "Plain" volume shows 101 GB.
The "LZ4" volume shows 9.1 GB used.
I'm trying to understand why "zdb -b LZ4" and the GUI are showing a compression ratio of 2.41%. How is it doing it's math?
Thanks.
[blah@nas-test1 /mnt]$ sudo zdb -b LZ4
Traversing all blocks to verify nothing leaked ...
loading space map for vdev 0 of 1, metaslab 66 of 116 ...
7.86G completed (1055MB/s) estimated time remaining: 0hr 00min 01sec
No leaks (block sum matches space maps exactly)
bp count: 173868
ganged count: 0
bp logical: 22589351936 avg: 129922
bp physical: 9362349568 avg: 53847 compression: 2.41
bp allocated: 9672335360 avg: 55630 compression: 2.34
bp deduped: 0 ref>1: 0 deduplication: 1.00
SPA allocated: 9672335360 used: 0.97%
additional, non-pointer bps of type 0: 24
Dittoed blocks on same vdev: 1714
The "Plain" volume shows 101 GB.
The "LZ4" volume shows 9.1 GB used.
I'm trying to understand why "zdb -b LZ4" and the GUI are showing a compression ratio of 2.41%. How is it doing it's math?
Thanks.
[blah@nas-test1 /mnt]$ sudo zdb -b LZ4
Traversing all blocks to verify nothing leaked ...
loading space map for vdev 0 of 1, metaslab 66 of 116 ...
7.86G completed (1055MB/s) estimated time remaining: 0hr 00min 01sec
No leaks (block sum matches space maps exactly)
bp count: 173868
ganged count: 0
bp logical: 22589351936 avg: 129922
bp physical: 9362349568 avg: 53847 compression: 2.41
bp allocated: 9672335360 avg: 55630 compression: 2.34
bp deduped: 0 ref>1: 0 deduplication: 1.00
SPA allocated: 9672335360 used: 0.97%
additional, non-pointer bps of type 0: 24
Dittoed blocks on same vdev: 1714