Thanks, and thanks also to everyone who replied.

Turns out dma was disabled.  With dma disabled, read/write rates
on the holding disk were a little over 3 MB/sec.

The dumper and taper reported different average performance, but
both were in the same ballpark, from 2.4 to 2.6 something MB/sec.
Not bad at all, considering the speed of the holding disk.

Thanks again to everyone who replied.

Roy Heimbach
--
Roy Heimbach 505-277-8348 / User Services / HPC@UNM
University of New Mexico, Albuquerque

On Fri, 16 Dec 2005, Gene Heskett wrote:

On Friday 16 December 2005 13:30, Joshua Baker-LePain wrote:

On Fri, 16 Dec 2005 at 1:08pm, Gene Heskett wrote

That almost sounds like he would need a dedicated hardware raid to
use as a holdng disk then.  Ouch. And maybe futile unless that same
controller can also handle the tape & library, in which case the
devices could negotiate their own transfers between themselves, at

I've got a 4 disk SATA RAID0 on a 3ware controller for the holding
disk.

And what speeds are reported by "hdparm -tT /dev/md0"?

whatever the limiting speed of the cable might be.  This library is
I take it, a scsi3 wide interface? 320mb/sec rated?

Yep.  In my case, the library is the only thing on the SCSI chain.

Which means the data has to piped thru the pci bus, so the maximum on a
non-pci-x buss is 133MB/sec.  And the average will be somethat less
than that when the handshaking is factored in.  But only 2.5MB/Sec
says there is a very small pinhole someplace its being forced through.