You might want to start with:
http://mailman.eng.auburn.edu/pipermail/veritas-bu/2002-July/011660.html
William Enestvedt writes:
> I have read with interest recent messages (and the Veritas web page
> at http://seer.support.veritas.com/docs/183702.htm) about tuning
> NET_BUFFER_SZ, SIZE_DATA_BUFFERS and NUMBER_DATA_BUFFERS for better
> performance...but now I realize I'm confused about which way I need
> to focus my attention.
On your overall throughput, assuming that's your ultimate goal.
> My environment is NBU 3.4 on Solaris (the Media Servers run 2.6,
> and the Master Server runs 8); each Media Server has a Sun L9
> library, which holds a Quantum 8000 DLT and nine tapes.
> In my bptm logs, I find the following entries side-by-side:
> ---- begin log sample ----
> 21:51:46 [29568] <2> fill_buffer: [29567] socket is closed, waited
> for empty buffer 3 times, delayed 3 times, read 4738656 Kbytes
> 21:51:46 [29567] <2> write_data: waited for full buffer 12820 times,
> delayed 135496 times
> 22:25:26 [29971] <2> fill_buffer: [29970] socket is closed, waited
> for empty buffer 19242 times, delayed 22981 times, read 9905792
> Kbytes
> 22:25:26 [29970] <2> write_data: waited for full buffer 9057 times,
> delayed 30164 times
> ----- end log sample -----
> Here's my questions:
> 1. Have I changed things for the worse or the better by following Veritas'
> suggestions and making the following changes?
> NET_BUFFER_SZ = 64k
> SIZE_DATA_BUFFERS = 64 k
> NUMBER_DATA_BUFFERS is left empty, defaulting to 8
Depends on what happened to your overall throughput, which we can't
see here.
> 2. Is it odd that some jobs wait for empty buffers, while other don't?
Not at all. Some jobs might come from faster disks and/or over
faster/less utilized networks, or be multiplexed with less other
streams (or with slower streams). Might have been a tape mount in
there also. Fulls will probably create data a lot faster than
incrementals.
> 3. What's the difference between the fill_buffer entries and the
> write_data entries? Do the write_data complaints about waiting
> for full buffers refer to the tape library going idle because NBU
> can't supply it with enough data? If so, then what do the fill_buffer
Yes.
> complaints about waiting for empty buffers refer to?
The opposite. The input side has to stop and wait for the tape drive.
> Thanks for any suggestions anyone can offer.
Definitely make sure you have correct st.conf entries for your tape
drives, and test restores any time you modify the SIZE_DATA_BUFFERS.
> -wde
> --
> Will Enestvedt
> UNIX System Administrator
> Johnson & Wales University -- Providence, RI
>
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--
Larry Kingery
"Cut down a tree with a herring? It can't be done!"
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