"Neulinger, Nathan R." wrote:
>That's interesting, are you multiplexing with multiple servers? Cause from
>limited testing, I've found that doing more than one vos dump at once to the
>same server doesn't actually increase your data rate any, or increases it
>only a tiny amount. If the disks on the server were the bottleneck, it would
>have a more noticable effect I'm sure.
We did a bunch of testing on this. The bottom line was that for epoch
dumps the magic number was 2 simultaneous processes (and it was not
tremendously better than 1). After that, yes, spindle (or other??)
contention hurts your performance more than parallelism increases it.
For incremental dumps (vos dump -t), we only tested up to six
simultaneous processes, and performance got better with each
additional process. Our best guess is that in the incremental case,
the vol server is spending alot of time looking for data to push out
the pipe, and so you get a significant benefit from parallelism there.
If I remember right, the performance lift we saw in the incremental
case (going from one dump to six) was a couple hundred percent.
Dave
