From: lancelot@spock.uucp (Thor Lancelot Simon)
Subject: Re: Slow writes to Ultrix 4.3 NFS server
Keywords: NFS server performance
Organization: Choate Rosemary Hall
Date: Mon, 16 Nov 1992 17:45:33 GMT

In article <leb.721782917@Hypatia> leb@Hypatia.gsfc.nasa.gov (Lee E. Brotzman) writes:
>john@iastate.edu (John Hascall) writes:
>>leb@Hypatia.gsfc.nasa.gov (Lee E. Brotzman) writes:
>>}I manage an SGI 4D/340 running IRIX 4.0.1 and a DECstation 5000/125 running
>>}Ultrix 4.3.
>>Anyway, several vendors' NFS servers mis-implement the standard (on purpose).
>>The NFS standard requires that writes be done "synchronously".  Some vendors
>>allow you to set an option which makes NFS writes be done "asynchronously"
>...
>>                     *** SGI ships their systems with ASYNCH as the DEFAULT ***
>>If you run asynch-writes (and we have modified our DEC servers to do this) and
>>you don't have them on a UPS you are running a massive risk.
>
>Our SGI box is on an uninterruptable power supply, but the DECstation isn't
>(it's in my office).  However we take electrical power seriously here at NASA,
>and we haven't had any major or even minor problems in our building since they
>finished some construction and totally replaced and upgraded our building power
>supplies.  It is not uncommon to have our computers up for months or even years
>between reboots, and then it's usually because of scheduled maintenance
>downtimes, not power problems.
>
>>The "safe" option to make your Ultrix boxes faster is to buy PrestoServe
>>for your NFS servers.
>
>Ahh.  The usual DEC solution is to charge their customers with add-on products
>that amend the original deficiencies.  We have been bitten the same way with
>our lousy tape device drivers for our VAX/VMS machines.

I've not exaactly got a reputation as a defender of the One True DEC Faith, so
I think I'm fairly safe in saying that this is unfair.  PrestoServe is a fine
product, and a much better solution (and most likely gives you better
performance, too...) than asynch-NFS; not offering asynch NFS as a kernel
option is a mistake, but DEC have posted unofficial, modified NFS object files
for most versions of Ultrix that _do_ provide it.  Having asynch NFS turned ON
by default, as SGI does, is irresponsible and dangerous, IMHO.  PrestoServe is
a product that greatly increases NFS performance _without_ the hazard involved
in asynch NFS, and it's a good one.  If it costs too much, fine.  Just don't
blame DEC for offering it!

Synch NFS is not a 'deficiency'.  Sun ship it, too.  Whether your installation
wants to trade safety for speed is an issue that should only be decided ONE
way when the OS is shipped -- for safety.  Remember, power's not the only issue,
unless you can honestly say you've seen a UNIX kernel that never panics...

That said, I do with DEC were more reasonable about configurabiliy of their
kernel, but hey, I object to any situation in which it's absurdly difficult/
expensive to get kernel source.  DEC aren't at the front of the pack, but they
aren't at the back of it, either.  This isn't VMS we're talking about here.

-- 
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*Thor Simon             * Okay, just a little pin-prick...There'll be no more-*
*tls@panix.COM          * Aieeeeaaaugh!-but you may feel a little _sick_.     *
*tls@spock.UUCP         *   ---Pink Floyd                                     *
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Newsgroups: comp.unix.ultrix