Thank you.
However I think it should be more clearly stated in zpool(1M) perhaps
even referring to compressratio and explaining that this one is
different, plus information as shown below how to get a dedupratio which
is similar in meaning to compressratio.
On 13/12/2009 11:44, Jeff Bonwick wrote:
It is by design. The idea is to report the dedup ratio for the data
you've actually attempted to dedup. To get a 'diluted' dedup ratio
of the sort you describe, just compare the space used by all datasets
to the space allocated in the pool. For example, on my desktop,
I have a pool called 'builds' with dedup enabled on some datasets:
$ zfs get used builds
NAME PROPERTY VALUE SOURCE
builds used 81.0G -
$ zpool get allocated builds
NAME PROPERTY VALUE SOURCE
builds allocated 47.4G -
Thus my diluted dedup ratio is 81.0 / 47.4 = 1.71.
Jeff
On Sat, Dec 12, 2009 at 10:06:49PM +0000, Robert Milkowski wrote:
Hi,
The compressratio property seems to be a ratio of compression for a
given dataset calculated in such a way so all data in it (compressed or
not) is taken into account.
The dedupratio property on the other hand seems to be taking into
account only dedupped data in a pool.
So for example if there is already 1TB of data before dedup=on and then
dedup is set to on and 3 small identical files are copied in the
dedupratio will be 3. IMHO it is misleading as it suggest that on
average a ratio of 3 was achieved in a pool which is not true.
Is it by design or is it a bug?
If it is by design then having an another property which would give a
ratio of dedup in relation to all data in a pool (dedupped or not) would
be useful.
Example (snv 129):
mi...@r600:/rpool/tmp# mkfile 200m file1
mi...@r600:/rpool/tmp# zpool create -O atime=off test /rpool/tmp/file1
mi...@r600:/rpool/tmp# ls -l /var/adm/messages
-rw-r--r-- 1 root root 70993 2009-12-12 21:50 /var/adm/messages
mi...@r600:/rpool/tmp# cp /var/adm/messages /test/
mi...@r600:/rpool/tmp# sync
mi...@r600:/rpool/tmp# zfs get compressratio test
NAME PROPERTY VALUE SOURCE
test compressratio 1.00x -
mi...@r600:/rpool/tmp# zfs set compression=gzip test
mi...@r600:/rpool/tmp# cp /var/adm/messages /test/messages.1
mi...@r600:/rpool/tmp# sync
mi...@r600:/rpool/tmp# zfs get compressratio test
NAME PROPERTY VALUE SOURCE
test compressratio 1.27x -
mi...@r600:/rpool/tmp# zfs get compressratio test
NAME PROPERTY VALUE SOURCE
test compressratio 1.24x -
mi...@r600:/rpool/tmp# zpool destroy test
mi...@r600:/rpool/tmp# zpool create -O atime=off test /rpool/tmp/file1
mi...@r600:/rpool/tmp# zpool get dedupratio test
NAME PROPERTY VALUE SOURCE
test dedupratio 1.00x -
mi...@r600:/rpool/tmp# cp /var/adm/messages /test/
mi...@r600:/rpool/tmp# sync
mi...@r600:/rpool/tmp# zpool get dedupratio test
NAME PROPERTY VALUE SOURCE
test dedupratio 1.00x -
mi...@r600:/rpool/tmp# cp /var/adm/messages /test/messages.1
mi...@r600:/rpool/tmp# sync
mi...@r600:/rpool/tmp# zpool get dedupratio test
NAME PROPERTY VALUE SOURCE
test dedupratio 1.00x -
mi...@r600:/rpool/tmp# cp /var/adm/messages /test/messages.2
mi...@r600:/rpool/tmp# sync
mi...@r600:/rpool/tmp# zpool get dedupratio test
NAME PROPERTY VALUE SOURCE
test dedupratio 2.00x -
mi...@r600:/rpool/tmp# rm /test/messages
mi...@r600:/rpool/tmp# sync
mi...@r600:/rpool/tmp# zpool get dedupratio test
NAME PROPERTY VALUE SOURCE
test dedupratio 2.00x -
--
Robert Milkowski
http://milek.blogspot.com
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