[Gllug] Performance Tweaking of SCSI tape drives

[Huw Lynes]

On Tuesday 23 July 2002 18:43, you wrote:
> On Tue, 2002-07-23 at 19:28, Huw Lynes wrote:
> > Hi All,
> >
> > 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.
>
> Oh stop boasting. Grin.
>
> Hate to say it, but I assume that you are talking about a
> PCI based Linux machine?

Yep its got an Ultra160 HV differential card. The PCI bus is capable of 
over 100Mb/s so I  don't see that as a bottleneck. Of course, I may be 
naive to think that. 

> Maybe the peak performance is only really achieved when you have
> a nice big SGI server :-)
> Of course THEN you need the fibre channel models. Grin again.

This DTF is one I half-inched of the back of an origin while no-one was 
looking. The best performance we've had out of it was 20Mb/s but that 
was on an Onyx. Admittedly in the Origin the Ultra160 card is in an XIO 
bus. But can that really be the difference? The data we are writing to 
the tape is comming of a Seagate cheetah which does 40Mb/s with no 
trouble. As I said earlier a 64bit 33Mhz PCI bus should be capable of a 
theoretical 266Mb/s, so surely 16Mb/s is not asking too much?

> Guess I'd start by looking at your SCSI controller.
> Is there anything in the READMEs in
>  /usr/src/linux/drivers/scsi
> about tweaking it?

I shall investigate tomorrow. Probably, I should not feel too bad given 
that the linux box costs less the 1/10 the price of the Origin and has 
so far shown 1/2 the performance. It's just that the tape drive is so 
expensive. Time to go home.

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



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