On Thu, January 20, 2011 12:28 pm, Silver Salonen wrote:
> On Thursday 20 January 2011 19:02:33 Paul Mather wrote:
>> On Jan 20, 2011, at 11:01 AM, John Drescher wrote:
>>
>> >>> This is normal. If you want fast compression do not use software
>> >>> compression and use a tape drive with HW compression like LTO
>> drives.
>> >>>
>> >>> John
>> >> Not really an option for file/disk devices though.
>> >>
>> >> I've been tempted to experiment with BTRFS using LZO or standard zlib
>> >> compression for storing the volumes and see how the performance
>> compares
>> >> to having bacula-fd do the compression before sending - I have a
>> >> suspicion the former might be better..
>> >>
>> >
>> > Doing the compression at the filesystem level is an idea I have wanted
>> > to try for several years. Hopefully one of the filesystems that
>> > support this becomes stable soon.
>>
>> I've been using ZFS with a compression-enabled fileset for a while now
>> under FreeBSD.  It is transparent and reliable.  Looking just now, I'm
>> not getting great compression ratios for my backup data: 1.09x.  I am
>> using the speed-oriented compression algorithm on this fileset, though,
>> because the hardware is relatively puny.  (It is a Bacula test bed.)
>> Probably I'd get better compression if I enabled one of the GZIP levels.
>
> Isn't the low compression ratio because of bacula volume format that
> "messes up" data in FS point of view? The same thing that is a problem in
> implementing (or using an FS-based) deduplication in Bacula.

I also use ZFS on FreeBSD.  Perhaps the above is a typo.  I get nearly 2.0
compression ratio.

$ zfs get et compressratio
NAME                                      PROPERTY       VALUE  SOURCE
storage                                   compressratio  1.89x  -
storage/compressed                        compressratio  1.90x  -
storage/compressed/bacula                 compressratio  1.90x  -
storage/compressed/[email protected]      compressratio  1.91x  -
storage/compressed/[email protected]      compressratio  1.91x  -
storage/compressed/[email protected]     compressratio  1.91x  -
storage/compressed/[email protected]     compressratio  1.91x  -
storage/compressed/bacula AT pre DOT pool.merge  compressratio  1.94x  -
storage/compressed/home                   compressratio  1.00x  -
storage/pgsql                             compressratio  1.00x  -

-- 
Dan Langille -- http://langille.org/


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