On Thu, Jan 23, 2003 at 02:46:07PM -0500, Scott Mcdermott wrote:
> Jon LaBadie on Thu 23/01 02:34 -0500:
> > >    - amanda can't do hardware compression without breaking easily
> > 
> > False.  Many use hardware compression very happily.  The issue is that
> > DLE's vary greatly in their compressibility.  Some of mine compress to
> > 20% of their original size, others to 95%.  For some tasks, amanda
> > would like to know how much tape a backup is going to use.  If she
> > doesn't compress it, she doesn't know for sure.  But she certainly
> > does not break.
> 
> ok "for some tasks" like what? If it doesn't break I'll probably opt for

planning, whether to do a level 1, level 2, or level 0 backup.  When HW
compression is used you will give a single "compressibility" factor for
her calculations.  That will only be accurate for some DLE's.

After a dump is done and in the holding disk, "will it fit" on the current
tape is also hard (impossible) to determine with certainty.  So you give
her an "approximate" capacity, guessing at an average compressibility and
she uses the actual dump sizes (precompression) and that guessed total
capacity in her calculatons for "will it fit".

> hardware compression, since that is a really big win for my particular
> site, and if I am using RAIT I get 4 ASICs working on it rather than one
> slow CPU :)

So do it, lots of people do.

> 
> > >    - amanda doesn't do parallel backups under any circumstances
> > 
> > Not sure what you are looking for in parallelism.  Certainly amanda
> > can simultaneously backup multiple DLE's from a single or multiple
> > clients.  Amanda can't run multiple configurations (say a daily and a
> > monthly config) at the same time.
> 
> I mean multiple drives.  Looks like RAIT is the answer here.  This
> feature is apparently backed out of the 2.4p2 RPM I have from Redhat
> 8.0; the ChangeLog note says "instead, in 2.5 and in 2.4 multitape" so
> this is why I did not come across it before.

Don't go with pre-built packages.  Get the current 2.4.3 source snapshot
and build it yourself.  RAIT was introduced in an early beta for 2.4.3.

> Amanda sure is a lot different than Legato Networker, which I am
> switching from :) But since we could probably pay enough full time
> workers to record all the bits needing backup onto a paper with a
> pencil, for less than it costs to keep Legato, I think I'll not mind a
> few setbacks on the way :)

Several years ago I moved two clients from Networker (Sun's version).
They have never looked back.  One client in particular was pissed at
Legato's claim (at the time) that because the backup host had died,
there was no way to recover any of the existing backups.

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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