Subject: Re: EDO RAM .... Help!
From: henry@zoo.toronto.edu (Henry Spencer)
Date: Sep 21 1996
Newsgroups: info.bsdi.users

> ok, then let me ask you this, why has most board manufacturers gone to EDO or
> other non-parity memory????  I don't want to get into a pissing contest, but
> get real, if the big guys (IBM, HP, Compaq), don't see a real need for parity
> memory, is what you are saying such a threat???

Didn't your mother ever say something along the lines of "if all your
friends jumped off a cliff, would you jump too?"?

The "big guys", like everyone else in the PC business, sink or swim on
selling crates and crates of cheap Windowboxes which mostly work to
corporate purchasing morons who don't know the difference between EDO and
IDE.  This is a market where a machine that has to be rebooted only once a
day is unusually reliable, where corruption of an occasional bit would go
unnoticed forever amidst all the errors created by inept programmers and
amateur spreadsheet writers, and where a fifty-dollar price difference can
make the difference between solvency and bankruptcy.

It is amazing that machines built for that environment will function at
all in an environment where we expect machines to stay up for months and
preserve every last bit properly for that time.  It's not at all surprising
that this is feasible -- at least, when loads are heavy -- only by picking
the hardware fairly carefully.

> You can quote all the technicality you want, I look at bonafide problems,
> todate, I've not had any problems...

You're missing the point -- how do you *know* you haven't had any
problems?  The whole problem with non-parity memory is that it doesn't
tell you when it loses a bit.  The odds are good that a randomly-chosen
bit won't be very important... but one day your number will come up. 

Modern memory is pretty good stuff and bit error rates are quite low.  But
that is not the same as zero, and there is something to be said for wanting
to hear about errors when they happen.

> I've also checked with BSD and they can
> state no system requirement that BSD must run on a system with parity memory.

There isn't any system requirement that any of the hardware be reliable.
The software will cheerfully do its best on any random piece of junk from
Garage Vaporboxes Inc.  It'll only crash or lose your data occasionally.

> ...Personally, I'll go with the people I've checked with.

Have any of them had to restore a gigabyte filesystem from backup tapes
lately?  I had to do that -- and a lot of other fancy scrambling -- last
week when a disk controller made a single tiny mistake that pyramided
rapidly.  The software is old (not BSDI) and wasn't quite careful enough
about recovering from controller errors.  One small error... and the
timing of the resulting downtime was so disastrously bad that some of the
administrative users were trying to decide whether to commit murder or
suicide.

If you don't think it's worth spending the money for a bit of simple
internal checking, I trust you do backups carefully and often.  It *can*
happen to you. 

                                                           Henry Spencer
                                                       henry@zoo.toronto.edu