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Re: [Networker] Performance Tuning backup
2007-07-26 11:21:35
egold AT fsa DOT com wrote:
> Hard to tell without a bit more information. How many of your tape
> drives are in use during the backup?
2 are in use.
How many sessions are being
> written?
8 sessions are being written.
> What is the observed write speed on each drive?
10 mb/sec, sometimes upto 15, but usually 10.
> What is the parallelism setting for the client?
it is set to 8 for parallelism.
> It's possible that lowering the target sessions may improve the overall
> speed, possibly at the expense of throughput on individual drives, but
> if there are not enough sessions or there is another bottleneck it might
> not help.
I do not think I have a bottleneck,
What an odd thing to say. If you didn't have a bottleneck somewhere in
the system you wouldn't have started this thread.
I would like to try tuning legato
first. These tape drives can write upto 50mb/sec or even more.
I expect they can. I have systems running multiple LTO-2 drives which
can often each achieve 40MB/s and above. However in your system you are
only throwing about 30MB/s at them, which is being divided equally
between 2 drives. The only things you can tune in NetWorker itself are
the target sessions and the various parallelism settings. If you
increased the target sessions here you would probably find that you get
about 20-30MB/s written on one drive only. If you decreased the target
sessions you would spread the 20-30MB/s over 4 or 6 drives, which
wouldn't be any help at all.
For some reason you are only managing to send 25-30MB/s to the server.
You haven't said whether this is a filesystem backup or whether you are
using the Notes module, but if you could send more data (which would
require a higher client parallelism as well as more available sessions)
you would possibly see better throughput. Of course there are lots of
reasons why this might not help, or even make things worse. The bigasm
tests should reveal a lot, and this should be your next step. With two
teamed GigE nics on the client you should be looking for a maximum
combined throughput of about 140MB/s which will still only keep 3 or 4
tape drives busy.
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