On Friday 20 September 2002 19:57, Michael Hannon wrote:
>Greetings. We've been happily running Amanda on a number of
> different systems around here for several years. Up to this
> point, we've always used a single tape drive (usually
> high-capacity) on each tape server. Now we're getting to the
> point where disk capacity is exploding. Tape capacity is
> increasing as well, of course, but it appears that we'll soon be
> in a situation where one large tape drive will be inadequate.
> Maybe we're there already.
>
>This has lead us to consider alternatives to our somewhat
> simple-minded approach to backups. One alternative would be to
> make finer subdivisions of the file systems that we back up (with
> GNU tar). I.e., instead of backing up simply:
>
> /home
>
>we might put separate entries in the disklist file for:
>
> /home/annie
> /home/bob
> .
> .
> .
> /home/zelda
>
>or whatever. That seems mildly tedious and probably would cause
> us at least to have to modify our number of tapes per cycle, buy
> additional tapes, etc.
Since the data itself isn't going to change/grow, only the
"housekeeping", I wouldn't think the expansion would be too notable
unless you not only have an annie, but an alice, 2 alecias with
variations on the spelling, ad infinitum.
>Another thought we had was to throw additional money at the
> problem and buy some kind of tape changer. But I have what seems
> to me to be a fundamental question about changers that I don't
> see answered in the FAQ's or .../docs, etc. I.e., if we have
> some kind of a tape changer, does it allow us to exceed Amanda's
> one-tape-per-session limit?
Conditionally yes. The condition being that no one disklist entry
can be larger than the tape, because the automatic changer advance
when it hits EOT on that tape causes it to advance the changer, and
restart that disklist entry on the next tape from square one.
> Can we make a single "virtual" tape
> out of multiple tapes in the changer?
Some changers claim they can, and mine does, but I have not ever
seen it work in practice here, nor do I need it, but my system is
only 46gigs, which amanda cheerfully uses about half a 4gig tape
per nightly run to back it all up on a 1 week dumpcycle.
> Or is it the function of
> the tape changer simply to let Amanda run unattended for as many
> sessions as there are tapes in the changer, but still using only
> one tape per session?
Once amanda has "optimized" her scheduleing, there is a chance that
one tape per session may well be enough. Thats so here, and the
main reason for the changer is so I don't have to swap tapes quite
as often, its a 4 slot magazine with a cleaning tape in the last
slot. At my age, I still tend to forget it, darn it. But there is
a "runtapes" argument in your amanda.conf which can allow amanda to
use 2 or more tapes per session *if* she needs to.
I'd think that rather than larger tapes, faster drives would be
higher on the list, if for no other reason than to get the darned
job done before the offices open in the morning. Here, it
occasionally is still running when the 4am stuff comes due, but
this DDS2 I use is a slower drive, less than 400kb/second.
Obviously a busier machine would need a faster drive. The upside
of the DDS2 is the price of the tapes, they are almost a non-issue
at less than 50 bucks a ten pack on ebay.
--
Cheers Mike, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
99.15% setiathome rank, not too shabby for a WV hillbilly
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