Paul Bijnens wrote:
On 2006-06-13 10:32, Toralf Lund wrote:
2. What happens to the holding disk file after a dump is partially
written to tape? Will Amanda keep the entire file, or just what
will be written next time around? And what if the holding disk
data is split into "chunks"?
Amanda keeps the entire dump, and will be flushed entirely again
on the next amflush or autoflush.
You mean entirely as in the whole DLE? That would mean that tape
splitting is restricted to multiple tapes written in the same run,
which would be rather disappointing.
Yes indeed. The whole DLE. A singe DLE still needs to be written
in one run, possibly using many tapes.
Oh no... Like I said, that's a big disappointment. I'm tempted to say
that it is not correct to claim that Amanda now suppots tape spanning,
if it can't span dumps across tapes written in separate runs.
Shouldn't it be able to delete the corresponding data from the holding
disk file as tape-chunks are successfully written - so that only the
remaining chunks would be flushed on the next run? Seems like this
should be easy enough to implement, especially if you interact with
holding disk chunks in a constructive manner. Is there any reason why
nobody has looked into this, except for lack of time?
But you may still split a veeeerrrryyyy large DLE into smaller ones
using the include/exclude mechanism that exists for a long time.
Yeah, I know, but hasn't the fact that you have to do that always been
seen as the one big limitation of Amanda? I was hoping this was gone now
now ;-(
This thing is, setting up the exclusions/inclusions right is nearly
always non-trivial on a system with dynamic data, and in a setup I'm
looking at now, it will simply be impossible to specify a static config
for this. Without real tape overflow support, we'll simply have to
update amanda.conf every day. The actual update may perhaps be done
automatically, but I was rather hoping I wouldn't have to implement a
tool for that, and the dump database etc. will obviously also get very
messy.
Differently put, I don't want to set up an amanda config which has the
odd DLE that's slightly larger than a tape - I want *all* DLEs to be
like that. I may be able to assume that they are never larger than two
tapes, so I could use "runtapes 2", but I fear that this would lead to
too much waste of tape space. I suspect the only way to get the full
dumps evenly split across a relatively limited number of tapes, will be
to set "runtapes" large enough for all full dumps to fit into one run,
but this is probably not possible in practice.
Only now you are not limited by the capacity of a single tape anymore.
Or maybe you misunderstood the question. Sorry if I was a bit
unclear, but I'm not sure what terminology to use, now. What do you
(should we) call one piece of output from the "tape split"? And what
should "dump" be taken to mean? The entire output from the backup of
one DLE, or one entry from the tape splitting. And what will a
holding disk file contain, anyway? Again, will it be data for the
whole DLE, or one instance of output from the split operation? (Like
I said, I'm testing a bit as I write this, but haven't been able to
draw any conclusions yet, mainly because I had to re-build amanda
just now...)
A piece of a DLE on tape: a tape-chunk. [ And so on ]
OK. Thanks.
- Toralf