[OT] NT, software reliability, and the lack thereof.

From: Eric Smith <eric_at_brouhaha.com>
Date: Mon Mar 15 14:21:06 1999

Dean Billing <drbilling_at_ucdavis.edu> wrote:
> After M-Squish designed NT, they hired one of the VMS gurus from DEC

No, they weren't *that* stupid. They hired him at let him design it.
The actual operating system deep in the bowels of Windows NT isn't so
bad. But they have lventy-seven layers of crap on top of it to keep
you from seing anything that might be simple and elegant.

> and while there have been many
> modifications to NT to add more VMS like features, it has one giant
> drawback, the underlying operating system is UNIX based, the Mach kernel.

No, it isn't. The underlying operating system is nothing like Unix, and
only vaguely like Mach (which are themselves two entirely different things).

However, as a "normal" Windows programmer (for the Win32 subsystem), you
can't even get to the operating system. You can only call the Win32
layer.

> Therefore, they have not been able to implement a true clustering system
> and IMHO because the DEC software engineers came late to the game, they
> were unable to design the basic reliability into the operating system
> software interfaces.

Again, that's not the fault of the kernel. The kernel is pretty good. The
problem is the leventy-seven layers of crap above it.

And the I/O architecture is even OK, but unfortunately you end up with
hundreds of device drivers written by bozos running at ring zero, so
naturally the system isn't as robust as it should be. DEC was in complete
control of the VAX, so most VMS sites didn't run any drivers that were
written by clueless morons.

But the worst problem with NT, and where the majority of the failures are
caused, is that for performance reasons starting with NT 3.5 (or was it 3.51?)
the moved the entire graphics subsystem (GDI) into kernel space. NT
immediately took a huge reliability hit.

> NT servers usually crash regularly, i.e. in less than
> a week, sometimes several times a day, especially if anyone is doing
> development work on them.

Um, what do you mean by "doing development work on them"?

If you want a file server to be as robust as possible, it should be used for
nothing but serving files. That was true even in the old days.

Nowdays people load all kinds of crap on their NT file server. It's no
wonder the things fall over every few days.

Of course, if NT didn't have the problems discussed above, it should have
been able to go weeks or months without falling over.

> Another drawback to NT is that many software
> upgrades and application installation/deinstallations require rebooting,
> something unheard of with VMS.

This problem is definitely a matter of poor design. I'm pretty sure this
one is also not the fault of the kernel, but of the leventy-seven layers
of crap above it. The programmers were too lazy and/or in too much of a
hurry to bother to figure out how to make changes without rebooting.

Note that all of my claims about NT architecture can be verified by
reading "Inside Windows NT". Except for moving GDI into the Kernel, which
happened later.
Received on Mon Mar 15 1999 - 14:21:06 GMT