[Gllug] Performance Tweaking of SCSI tape drives

[Kim Hawtin]

On Tue, Jul 23, 2002 at 07:58:34PM +0200, John Hearns wrote:
> On Tue, 2002-07-23 at 19:28, Huw Lynes wrote:
> > I'm currently playing with a Sony DTF-2 drive. I've got it up
> > and running using mt, tar and the standard st driver. At the
> > moment I'm getting about 8Mb/s write speed. I know the drive
> > should easily be capable of twice that.
 
> Can you tell us the configuration of the server you are using?

that'd help =)

> I'm clutching at straws here, but maybe the DTF will only achieve
> max performance when it is on its own SCSI controller, not the one
> with the disks on.  Or maybe I'm wittering and I've forgotten
> everything I ever thought I knew.  Someone please wallop me with
> the clue stick - its far, far too long since I've had to touch a
> SCSI cable or a tape.

you may need to check that the SCSI controller is actually talking
to the tape device at the full speed that the tape drive can...
ie if the SCSI controller is set to talk to the device at 5Mbits
then thats it, ive not seen any UW tapes for some time so maybe it
peaks at 10Mbits. 

it is possible that the higher figure you mention is with software
compression. so its actually only transfering max 10Mbit over the
SCSI bus, but say 16Mbit of data but in compressed form...

some tape drives have hardware compression on the driver but that
too is limited by the speed of the SCSI bus for the device.

yours,

Kim
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