Gents? Anything?

On 6/14/07, Khurram Tariq < khurramtm AT gmail DOT com> wrote:

Well the guide doesnt say max values, its just that values till 256k are printed in a tabular format and there's no mention of being able to put in values higher than that. What about the number of data buffers? Anyone using a number greater than 16?

Most of my systems are Solaris 9 boxes with 4GB to 64GB memory so I'm not worried about the memory contention since there's only a limit to the multiplexing and multistreaming one can do and after that the data rate does not increase so using the formula in the guide I should be consuming 32MB of memory with the backups. (16 buffers of 256k *2 drives * 4 multiplex)

By the way In my case I've found out that 2 x FC LTO3 drives with multiplexing and multistreaming gets me the best performance (reached a max of 170MB/s) and adding more drives and streams does not increase the total speed. Any pointers here?

Regards,
Khurram

On 6/14/07, bob944 < bob944 AT attglobal DOT net> wrote:

> I was wondering what are the max values one can put in the files
> SIZE_DATA_BUFFERS & NUMBER_DATA_BUFFERS. The NetBackup 6
> Tuning Guide talks
> about max values of 256kb and 16 respectively.

I don't remember it saying that.  Anyway, maximum size is whatever your
OS and system settings and tape driver and hardware support--many
Windows systems are limited to 64KB by the miniport driver, for
instance.  You find out by experiment, the most important experiment
being to restore.

Max number is whatever it takes for the shared memory request to be
denied, in which case NetBackup will report a status 89.

Unless you have some very exotic OS/hardware, large values for either
are usually a waste of memory and limit the number of jobs you can run.
"Large" being, say, 512KB or 512 buffers, as I've never personally seen
either of those values perform beetter than 256 of each, regardless of
the setting of the other parameter.

Controlled, documented testing, varying one thing at a time, using the
guidance in the tuning guide, should get you there.  BTW, the defaults
used in NetBackup 6 are sufficiently better to warrant getting rid of
your touch files and see how it works out.  The defaults are also
described in the tuning guide.