Great article. I appreciate the pointer. I have seen a lot
of studies by Bill Ham over the years; much of it doesn't get
published, so it is nice to see this one. He is 'da man' of
SCSI physical design and has had a lot of input to the T10
committee over the years. Another document by him that is worth
looking at for the serious SCSI hardware geek is:
SCSI Enhanced Parallel Interface (EPI) Technical Report
ftp://ftp.t10.org/t10/drafts/epi/epi-r16.pdf
Bill Collins wrote:
>
> A company I fondly worked for published technical journals which included
> an article on this subject, http://www.digital.com/DTJR01/DTJR01HM.HTM. :-)
> Those who still have their collection can refer to "Digital Technical
> Journal", Vol 9 No 3, 1997.
>
> Bill
>
> On Mon, 14 Aug 2000, Dan Jones wrote:
> > There is electrical and then there is electrical. In theory, it is a
> > bad idea to remove or add a SCSI device while a transfer is taking
> > place. Why? Basically, the capacitive load on the SCSI bus changes
> > when drive contacts are made or broken i.e. the transmission line
> > characteristics of the bus change and that affects the signal in
> > flight. Since transfers during the data phase are only protected by
> > parity, undetectable errors might occur.
> >
> > Having said that, empirical evidence points to this type of failure
> > being exceedingly rare for older versions of SCSI with restricted
> > configurations and qualified components. Personally, I take
> > the approach that something I can't prove won't happen...can happen
> > and most likely will.
> >
> > Some people take the opposite view and they are mostly happy most of
> > the time. :)
> >
> > [ ... ]
> --------------------------------------
> William Collins
> Department 04618, Scientific Computing
> 880/D10E1, (505)844-9414
> [EMAIL PROTECTED]
--
Dan Jones, Manager, Storage Products VA Linux Systems
V:(408)542-5737 F:(408)745-9911 1382 Bordeaux Drive
[EMAIL PROTECTED] Sunnyvale, CA 94089
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