> On 08/26/10 05:04, me AT free-minds DOT net wrote:
> > Hello,
> > I think this is a common question but i didnt found a proper answear
in
> > the documentenation, if there is already one please let me know :)
> >
> > So we have now successfully set up our Bacula Servers and everything
is
> > now running more or less...
> > But we have some questions:
> > 1) do we really need to spool? We are not writing to real tapes, we
have a
> > filesystem as backend (ext3 over glusterfs).
> 
> If you're using a disk backend, honestly, there is really no reason
> whatsoever to use spooling. 

A small spool (eg a few GB) is useful to avoid fragmentation on your
backup disk. It will slow down the backup a bit, but not as much as
you'd think if the spool is fast (eg flash or 10KRPM disks) and the
backup medium is slow (eg USB2 attached). Fragmentation on backup media
when you are doing more than one concurrent backup very quickly reaches
several 9's.

A hdparm on my USB2 attached 5400RPM 2.5" backup disk maxes out at
31MB/second read performance. That's slower than any current tape drive.
hdparm on the 7200KRPM RAID5 disk array (admittedly, read speed and not
write but half the time you are reading the spool at least) is
350MB/second. Over 10x the speed.

If the backup disk was eSATA attached and 7200RPM or faster then the
performance impact of spooling would become more pronounced but at the
moment it's insignificant.

James

------------------------------------------------------------------------------
Sell apps to millions through the Intel(R) Atom(Tm) Developer Program
Be part of this innovative community and reach millions of netbook users 
worldwide. Take advantage of special opportunities to increase revenue and 
speed time-to-market. Join now, and jumpstart your future.
http://p.sf.net/sfu/intel-atom-d2d
_______________________________________________
Bacula-users mailing list
Bacula-users AT lists.sourceforge DOT net
https://lists.sourceforge.net/lists/listinfo/bacula-users