Hello list,

     The data center in which I work recently purchased a Spectra Logic 
T380 and T200 tape library running IBM LTO-4 tape drives for our local 
and remote site, respectively. After zoning the libraries in, installing 
the device mappings files from Symantec support and what not, I decided 
to test some backup and restores, only to get terrible throughput. My 
Spectra Logic field tech informed me that I should be able to expect a 
theoretical upper limit transfer rate of about 120 MB/s. I'm getting 
anywhere from 9 MB/s to 50 MB/s.

     I tried adjusting the SIZE_DATA_BUFFERS and NUMBER_DATA_BUFFERS per 
the Netbackup tuning guide, and that helped me get up towards the 50 
MB/s rate, but that's still a little under half what I should be seeing.

     I've opened cases with Symantec and Spectra Logic. The latter had 
me download the ITDT tool from IBM and we ran some basic tests going 
straight from my Linux master server to a drive on the library. We 
consistently achieved around 110 MB/s throughput. IBM unfortunately 
never wrote a version of ITDT for Tru64, so I logged a call with HP and 
we've been using the time and dd command to calculate how long it takes 
to write zeroes to a tape, like this:

/bin/time dd if=/dev/zero of=/dev/ntape/tape16_d1 bs=60k count=1361163

I've tried tape16 and tape16_d1 device special files, and we're 
consitently getting around 50 MB/s throughput. If I issue the same 
command, but of to /dev/null, the command runs in a few minutes, so I'm 
pretty sure my server can handle the load.

My question is this: Does anyone out there use Tru64 with LTO 3 or 4 
drives? If so, what kind of throughput are you getting and (if you're 
getting better than 50 MB/s) did you have to perform any weird voodoo to 
get that throughput?

Thank you.

- Heathe Kyle
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