Subject: Re: VAX 6460 being slow, IO bottlenecks and SMP woes ...
To: Gunther Schadow <>
From: Paul Thompson <>
List: port-vax
Date: 03/20/2002 20:41:59
On Wed, 20 Mar 2002, Gunther Schadow wrote:

> So I looked at statistics. Nothing paged out (0.5 GB of RAM),
> but looks like the system is heavily I/O bound and I/O
> is quite slow. I even distributed disk load over 3 RA90, though all on
> the same controller, but at least that's a KDM70, directly on the XMI
> bus. Still, disk access seems just a bit on the slow side. Why?

The RA90 is not a speed demon at 3600 rpm and SDI seems to max out under

      RA90,        fixed-media 9" DSA disk drive

            Capacity ... 1.216 GB, 2376153 total blocks

            2,649 cylinders, 13 tracks/cylinder, 69 sectors

            peak xfer rate ........... 2.77 MB/s
            spiral xfer rate ......... 1.72 MB/s
            average access time ..... 26.8 msec
            average seek time ....... 18.5 msec
            track-track seek time .... 5.5 msec
            head switch time ......... 3.0 msec
            average latency .......... 8.33 msec
            rotational speed ...... 3600 RPM
            request rate ............ 39 I/Os per second at 50 msec response time
                                      46 I/Os per second at 100 msec response time

> It's interesting. At some time soon, may be early this summer,
> I'll give a VAX party where one of the highlights will be a
> race between my i486/33 and the 6460 in compiling something,
> there we can see if it's really just my perception that the
> 6460 is kind of slow for the price, even measured by past
> standards.

Wouldn't the 65xx or 66xx be more around the time of a 486? I don't know
when the 64xx came out but I thought it was earlier.  Are you planning to
run a *bsd on the 486 from the same timeframe as Ultrix 4.5 or one with a
scheduler and interrupt handler potentially more recently optimized?

Does your i486 feature long ribbon cable to dual ported IDE drives to
support its clustering?  If not, perhaps you were paying for features
other than speed, ones that Ultrix took less advantage of than VMS.