On Tue, Aug 31, 2004 at 10:42:58AM -0400, Joe Konecny wrote:
> The system is set up to accept
> any tape and run a full backup. What we do is keep the tapes
> in rotation and if someone forgets to bring a tape back from
> off site it is no big deal we just use the next one.
This is the interesting part. Amanda tries to protect you from
accidentally overwriting backups that you wanted to keep. To
that end, it won't "accept any tape", but only tapes whose
contents it considers to have expired. That's what the whole
"tapecycle" thing's about. To get what you want, you'll have to
defeat this protection.
Typically, people have C tapes, and set "tapecycle" to C. Under
those conditions (once you've reached equilibrium by running
through all the tapes once) Amanda refuses to write to the C-1
most recently used tapes; it will only accept the least recently
used tape, C, or a new tape that's never been written to. That's
the situation I'm familiar with.
But suppose you have more than "tapecycle" tapes, i.e. you have T
tapes for some T>C. I believe (please correct me if necessary,
folks) that in this case, Amanda will still refuse to write to
the C-1 most recently used tapes, but will accept any of the
older ones, i.e. any of tapes C through T. It'll say "The next
tape Amanda expects to use is: [label for tape T]", but that's
not quite true; in fact, it'll accept any tape that isn't in the
range [1, C-1].
So, to get the behaviour you have now, I think you can just set
"tapecycle" to 1. But I don't know for sure, because I'd never
do that :-) Personally, I *like* it that Amanda protects me from
my own mistakes (forgetting to change the tape, or mounting the
wrong one, for example).
Of course, you could use a hybrid approach and get yourself some
protection against accidents, but also some of the flexibility
you want, simply by setting "tapecycle" to something like 5;
then, the latest few tapes would be protected, but any of the
older ones would do.
> Arcserve
> assigns each tape a new ID when it uses it.
This, Amanda won't do. You assign each tape an ID (i.e. label)
when you amlabel it, and Amanda uses that same label forevermore
(unless you manually relabel the tape of course, but Amanda
discourages that).
That difference in detail shouldn't cause any problem in meeting
your basic requirement, though.
> We write the date
> of the backup on the case of each tape. If a restore is needed
> we figure out what date we want and insert the tape. Arcserve
> will tell us the tape ID and then we can restore from that
> session.
In the Amanda world, you wouldn't need to write the backup date
on the case. To restore, you'd:
- figure out what date you want
- use amrecover's "setdate" command, specifying that date
- amrecover would tell *you* which tape to mount, asking for it
by its label
- should you ever switch to doing incremental backups instead
of full ones every night, or should your backups grow to more
than one tape per run, amrecover might need more than one
tape to do a multi-file restore; it'll ask for each one in
turn, again by label
--
| | /\
|-_|/ > Eric Siegerman, Toronto, Ont. erics AT telepres DOT com
| | /
It must be said that they would have sounded better if the singer
wouldn't throw his fellow band members to the ground and toss the
drum kit around during songs.
- Patrick Lenneau
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