On Fri, 10 Jul 2009, Heathe Kyle Yeakley wrote:

> I'm curious:
>
> 1) Where may I get a copy of this paper?
>
> 2) Does the paper list exactly how they went about performing their test?
>
> Right now I'm tuning a DR environment. I mail tapes to my off site facility, 
> phase 1 and phase 2 import my images in and then restore. Other than that, my 
> Master, Media, clients and libraries just sit there. So I've eliminated the 
> factors of "Is there other stuff running that could impact performance".
>
> Furhtermore, according to page 106 of the Netbackup Performance and Tuning 
> Guide:
>
> "IMPORTANT: Because the data buffer size equals the tape I/O size, the value
> specified in SIZE_DATA_BUFFERS must not exceed the maximum tape I/O size
> supported by the tape drive or operating system. "
>
> Where do I go to find the tape I/O size? And where do I find the tape I/O 
> size supported by the tape drive and OS? My configuration is:
Windows (earlier versions had an issue where the driver could only do 64k) 
that is probably what it is referring to.

>
> Tape Drives: LTO-4 IBM
> # or drives: 6
> Master Server OS: RHEL
> SAN Media Server: Tru64
> Library Vendor and Model: Spectra Logic T380
>
> Would Red Hat, IBM, Spectra Logic or the LTO site have the supported tape I/O 
> size numbers?
>
> Thanks.
>
> - Heathe Kyle Yeakley

After you read many of the white papers and perform testing, you will find
what best works for your environment:

Here you go though, as you asked for it, page 39:
http://www.sundds-lto.com/uploadLinks/Gen3_Performance_Wpaper_OEM_AQ_Feb05_final.pdf

Some other/more info:
http://h71028.www7.hp.com/ERC/downloads/5982-9971EN.pdf

In addition, most backup application software allows the block size on tape to 
be changed. For all HP StorageWorks Ultrium 960 backups, HP recommends the tape 
block size/transfer size be configured to 256 KB.

In general, (IMO) in my environments I find 256kb with 32 buffers optimal for
LTO-4 drives, as you have in your environment.

Once you pick your size_data_buffers, you want to keep them the same.
Most people tune to 256k and are good.  I have seen 90-93MiB/s with that
setup on LTO-3 (uncompressed) and sending compressible data I have pushed
127-130MiB/s.

Justin.

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