On Thu, 21 Sep 2017 16:58:09 +0200, Gandalf Corvotempesta <[email protected]> wrote:
>> It's ok to change the compression level (eg, from 3 to 1).
Notice that compressing a already compressed file, whatever
compression level used in the first compression, will not save
any space. So using compression level of 1, 3, or even 9,
compression it again will give almost no compression gain.
> I'll go with compression 0. ZFS is compressing, there is no need to
> add an additiona layer.
Backuppc compression should be more efficient, as it
compress the file instead of disk blocks and most of the time, file size
do not match the disk block size. Add this to the fact that the
zfs compression block is usually 128k and in gzip is dynamic and can be
much, much larger. Finally backuppc uses zlib and zfs usually
uses LZ4, but even if you set it to uses zlib, it usually waste more cpu
compressing unused block data and due the block size difference, it
compress less:
https://superuser.com/questions/562381/why-is-zfs-gzip-9-compression-so-much-worse-than-actually-using-zip-files
So if this is a dedicated partition for backups and specially
for backuppc (as its compression usage is very efficient), i would
recommend disable zfs compression and use backuppc compression. If
you are using the partition not only for backuppc, then you need
to check if you prefer a faster and flexible but weaker compression (zfs)
or a less flexible but more efficient compression (backuppc zlib). Also
notice that you can create several zpools, one with compressions and
other without
good luck
higuita
--
Naturally the common people don't want war... but after all it is the
leaders of a country who determine the policy, and it is always a
simple matter to drag the people along, whether it is a democracy, or
a fascist dictatorship, or a parliament, or a communist dictatorship.
Voice or no voice, the people can always be brought to the bidding of
the leaders. That is easy. All you have to do is tell them they are
being attacked, and denounce the pacifists for lack of patriotism and
exposing the country to danger. It works the same in every country.
-- Hermann Goering, Nazi and war criminal, 1883-1946
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