[rescue] Re: Re: how to utilize multiple tape drives in the same library/silo with Amanda...

[Robert Novak]

On Mon, 22 Jul 2002 nick at snowman.net wrote:

> Sure, no problem.  I too prefer haveing a cache disk, and every serious
> backup system I've configured has one.  Amanda requires one at *least* the
> size of your largest partition to be backed up.  There's a slight
> difference between requireing a cache drive and requireing the entire
> partition get backed up to the cache partition.

Well, for what Amanda is doing, there's no other way. It's writing the
tar/dump output to disk, then compressing it and putting it to tape (if I
recall correctly... maybe it's compressing the tar/dump output to disk,
then writing it raw to tape?)). You could try hacking it to do a
stdin/stdout split into blocks (kinda like what Networker used to do) but
that would be messy.

As of about 3 years ago (I think) you could specify your compression ratio
and get away with a smaller partition. So my backup set was consistently
compressed 50%, my largest filesystem was 100GB, I had a 55GBish staging
disk. 

However, it's painfully obvious that to store an archive on disk you have
to have enough disk to store the archive. Can we at least agree on this?

If you're using a commodity server and your reliability requirements are
suitable, this would be a good place to put an IDE disk in place, or a
couple. I'm actually picturing a couple of cheap 60gb disks on a hw raid
card as a staging disk.

--Rob


Robert Novak, Indyramp Consulting * rnovak at indyramp.com * indyramp.com/~rnovak
	"I don't want to doubt you, Know everything about you
      I don't want to sit Across the table from you Wishing I could run."