[Gllug] Performance Tweaking of SCSI tape drives

Huw Lynes huw-l at moving-picture.co.uk
Wed Jul 24 07:55:29 UTC 2002

On Tuesday 23 July 2002 19:31, you wrote:
> 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.
> 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.

How do I check that?

> 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...

It seems unlikely. On the SGI boxes we talk to the tape using mt and 
tar. And I should have written MB not Mb as I was talking about bytes 
not bits. 

| Huw Lynes               | The Moving Picture Company  |
| System Administrator    | 127 Wardour Street          |
|.........................| London, W1F 0NL             | 

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