On Fri, 2005-04-01 at 13:09 -0500, Gene Heskett wrote:
> On Friday 01 April 2005 03:19, Erik P. Olsen wrote:
> [...]
> >Hm. I would like to challenge this statement. It may be true if you
> > have a large network of systems to back up but if you only have one
> > system I doubt if it's true. Before my switch to Linux I backed up
> > my system (OS/2) on a weekly schedule with one full back-up and
> > four incremental back-ups to one tape only.
>
> If useing tapes, and they are big enough, set the holding disk
> reserved value to some low percentage like 20%, and only put in a
> tape once a week, with the autoflush option set in your amanda.conf.
> That will put the whole weeks worth of backups on one tape. It does
> have the disadvantage of leaving that weeks stuff subject to a disk
> failure though. But thats something I've not had in about 2 years,
> no failures out of about 7 drives here when they are all spinning.
> But I'll lose one yet today just because I mentioned it, Murphy is
> listening. :(
Last year I had head crash with my two 60 GB disks when they where still
under warranty. I had them replaced but couldn't wait the 3 weeks it
took, so I had to buy new ones. Last time it happened (there were 6
months in between) the tape streamer also died and took the tape with
it. I'm sure Murphy has a law for that. As a consequence I could not
restore the system even with a new and well functioning tape station in
place. Statistically this problem should never occur, but it did.
>
> > It worked extremely
> > well, if I crashed my system - which I did very often - it took me
> > about half an hour to recover either using a stand-alone recover
> > program or my maintenance OS/2 if it was alive and I kept an
> > archive of up to 8 weeks of back-ups.
>
> I was always told that OS2 was stable. And I stay quite bleeding edge
> in terms of the kernel I run on this FC2 system, which is also
> backing up my RH7.3 firewall box. Currently running 2.6.12-rc1, the
> smoothest running, snappiest kernel yet in the 2.6 series. I can't
> recall the last time I actually crashed a running system. Several
> months ago in any event.
OS/2 is stable though not as stable as FC3. The frequent crashes were
mainly because I did a lot of testing with new system software.
>
> > Now with Linux and Amanda I
> > use 9 tapes mainly because Amanda won't add today's back-up to
> > yesterday's tape.
>
> Thats a security risk amanda won't take. When amanda is done, and has
> released the drive, there is nothing to prevent someone from removing
> the tape, and either reinserting it, in which case the tape is
> rewound and will be totally overwritten, or even the wrong tape might
> be reloaded. Either way, amanda has no ironclad assurance that the
> tape will be sitting in the same position it was left in, ready to
> append new files to it. Yes, most drives today can do an 'mt
> -d/dev/nst0 seof' and hit within a quarter of an inch of it. But
> some drives cannot, and that locks amanda out of useing that feature
> for all users. At some point, the last legacy drive that cannot do
> that might die, but we have no idea when that might be...
I suppose the back-up software placed a sort of end-of-tape mark after
each back-up and just searched for that tapemark when a new back-up was
about to be run. I've used it for 5 years and it never failed. It would
even ask for another tape to continue the back-up if the first tape ran
full.
>
> Maybe that should be the subject of a questionaire at some point?
>
> > I could probably do with less tapes but I feel
> > more confident with a large tape pool.
>
> [...]
>
> I answered this in a previous post.
>
--
Regards,
Erik P. Olsen
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