Oops, I should have sent my reply to the list.

On Fri, 28 Jan 2011 16:35:05 -0500
Joe Konecny <[email protected]> wrote:

> On 1/28/2011 2:11 PM, Charles Curley wrote:
> > For now, with 100 GB of data going to a 1 TB hard drive, you can
> > probably back up to that hard drive. But not for long. Two caveats:
> >
> > * Having your data, holding disk, and vtapes all on the same drive
> > will result in lots of disk drive thrashing. Ideally, have each on
> > their own drive. Short of that, eventually go to a separate drive
> > for the vtapes.
> 
> My data would be on a different server than the vtapes.  Does a
> holding disk make a big difference if you are using vtapes?
> 
> 

Yes. vtapes emulate a tape to the point that amanda won't write to them
in parallel, just as it cannot write to a tape in parallel. A holding
disk lets amanda always have one or more DLEs ready to go to the tape.
While shoe-shining obviously isn't an issue with vtapes, that one DLE at
a time requirement is a bottleneck.

There is an effort to allow one configuration to write to multiple tape
drives (including vtapes), but I don't know its status. That might move
things along fast enough to reduce the need for a holding disk, but I
haven't played with it.


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