Hello Bryce,

Am 14.02.2014 00:36, schrieb Bryce Nordgren:
> Hi all, 
> 
> I’m setting up bareos as a backup solution for my large (60TB) RAID. I’m 
> backing up to another 

RAID on a different machine, and the File Daemon and Storage Daemon are 
connected by GbE.
> 
> The setup works well. With no software compression, I’m maxing out the GbE 
> link, 

sustaining 117 MB/s (10^6 *bytes/sec).  I’m looking into compression because

7.4Tb takes almost 18 hours to backup, and there will be more. With compression,

I have a question: When Bareos reports “[FD|SD] Bytes Written”, is this is a

post-compression value? (e.g., the number of bytes read by the FD is larger by 
the

“Software Compression” percentage, correct?)


Yes, the calculation of the compression value is

compression = (double)100 - 100.0 * ((double)jcr->JobBytes / 
(double)jcr->ReadBytes);

, where

   uint64_t JobBytes;                     /* Number of bytes processed this job 
*/
   uint64_t ReadBytes;                    /* Bytes read -- before compression */

(see dird/backup.c and include/jcr.h)

> 
> The short version is: assuming the above, it looks like my “effective backup 
> rates” (Bytes read by the FD/sec) is:
> 
> No compression: 117Mb/sec (100%)
> GZIP: 65.82 Mb/sec (56%)
> LZOFAST: 236.44 Mb/sec (202%)
> Pigz [1] projection: 532.76 Mb/sec (454%)


you could also try lz4, lz4hc and lzfast.

> 
> That last bit is a projection based on comparing the Parallel Implementation 
> of GZip (PIGZ)[1] 

to the standard gzip on my system. I started messing with parallel compression 
because I

noted that during a GZIP run, my 24-thread system was ~95% idle. It is 
interesting to note that

PIGZ compiles against versions of libz found on RHEL/CentOS/SL 6 machines.
> 
> I would like to submit a feature request for PIGZ support on Linux-based FDs, 
> but I wanted to 

run it by the group first. It produces GZIP-compatible output files, it just 
does the compression

in parallel if you have an SMP machine. (I checked by compressing with PIGZ and 
uncompressing with
gunzip.)
> 
> Thanks,
> Bryce
> 
> [1] http://zlib.net/pigz/
> 

What you can always do is split your fileset into chunks and run backups of 
each one in parallel.


Best regards,

Philipp



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