Subject: ballpark ratio users:cpu for a [345]86 NetBSD box?

From: George Michaelson <[email-masked]>

Assuming sensible VLB/SCSI disk controller, and reasonable memory,
what are tenable numbers of interactive users on a NetBSD PC architecture
box doing mail/news stuff, both logged in and via inetd daemons?

reference points:

	DEC 5000/240 64Mb memory, seems to max out around 70 users
	Sun 600(2cpu) ditto

I estimate 3-4 procs per logged in user, 1 per inetd client so that
means 300 processes seems to be where the knee comes in for RISC
boxes.

(we're serving around 500 active users on these platforms, out of 3000
 candidate logins. Yep... 2500 sleeping accounts who've never logged in
 they are probably the POP/NNTP access load however)

Rubbery figures welcome. I guess that a 66Mhz 486 with 32+Mb can handle
around 40 interactive and a background load of the same net-users. PCI
Pentium should be more like the bigger boxes. Am I pessimistic?

Sorry if wrong list.

-George

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From: George Michaelson <[email-masked]>

> Pentium should be more like the bigger boxes. Am I pessimistic?
  
    I'd be shocked and amazed if you got any more than 12-18 people on a
  486/66 with 32+mb.  They just don't have the I/O for it.  As much as I
  love NetBSD/i386 (I have two intel machines that I built especially for the
  purpos of running NetBSD) the PC is simply not a multi-user platform.

Ok. so a pentium with PCI and a 32bit ethercard? 64mb memory? if I have
PCI scsi, and wide ether access, might this be plausible?

Note, the cost in AU dollars now exceeds amazingly discounted suns or
maybe even smaller AXP systems. This depressing is :-(

-George

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From: Dave McGuire <[email-masked]>

Regards,
                            -Dave McGuire
                             Operations
                             Digital Express Group, Incorporated
                             [email-masked]

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From: Dave McGuire <[email-masked]>

> PCI scsi, and wide ether access, might this be plausible?

  That would most certainly be more reasonable...But the thing is...if
you're gonna spend a buttload of money on new hardware, why not buy
hardware that's designed to support lots of users in the first place?
PCs are designed to give *great* performance to one person.  Big
servers are designed to give *good* performance to a LOT of people.
Sure, a big Pentium box running NetBSD would doubtless make an
excellent platform for software development, or perhaps as a big
nameserver or authentication server or something like that.  But try
to put a pile of users on it, and I think you'll be disappointed.  A
big studly Pentium/PCI box that you described is a wonderful piece of
hardware, I'm sure.  But for how much money?  I can pick up a Sun4/470
for about US$2,000.00 right now, that I know from experience (I work
for an Internet provider that sells shell accounts on Sun4/400-series
systems) can readily handle 60 people with no problem.

  I'm not meaning to flame here, so please don't take what I'm saying
the wrong way.  It's just that, in my opinion, you'd be wasting your
bucks...buy big fancy Pentium/PCI/NetBSD boxes for your engineers'
desks.  They'll love 'em.  Put big Suns, big (newer) VAXes, or even
big Alphas in your computer room for lots of users.  *They'll* love
'em.

> maybe even smaller AXP systems. This depressing is :-(

  True... :-( But...I have a 386DX/40 w/16mb RAM and an old 300mb ESDI
disk here-- and I must say that I'm constantly impressed by its
performance.  A PC, no less!  An old, cheap PC!  Useful again! :) :) I
can't wait to see NetBSD on a Pentium...

                            -Dave McGuire
                             Operations

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From: Dave Cornejo <[email-masked]>

I know an FTP session is not quite the same as a shell, but I have
seen a 486dx2-66 run >100 FTP session plus 10-15 shells at the same
time using FreeBSD.  I would assume that NetBSD would approximate
those figures.

-- 
Dave Cornejo                                There is nothing so subtle
Dogwood Media                                           as the obvious
Fremont, California

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From: Dave McGuire <[email-masked]>

On September 27, you wrote:
> Pardon, but a Pentium with a PCI bus has far better context switching,
> far better IO, and far better speed. What is left that the Sun 4/470,
> which was designed as a server, not as a multiuser machine (which is
> why it has too few MMU contexts) can beat the Pentium machine on?

  I'd argue that.  I will freely admit to having never *tried* to put
60 people on a PC, because the idea is just plain silly in my opinion.
The 4/400 CPU has 64 contexts, the largest number in the sun4 series
excluding the 4/600 (different animal altogether) and as such does
indeed make a wonderful multiuser machine.  That I *have* tried.
Again, I'm not trying to start a flame war here, so please don't turn
it into one.

> I can also pick one of those up in a reasonable configuration for
> $2,000.

  Really?  Now *that* comes as a surprise to me.  If they're down that
low these days, I think I might have to look into it.  That'd be quite
cool.

> Its not quite the same O/S or application, but I'll note that
> Compuserve has been successfully experimenting with hundreds of users
> on single PCs running BSDI.

  This I would like to see.

> The main problem I could see with a NetBSD Pentium box right now is
> that NetBSD won't max out the disk because the clustering stuff isn't
> in yet. However, the hardware is as capable as anything you can
> find. The Pentium is an UGLY chip in terms of instruction set, but the
> notion that the machine can't compete is misplaced. Try a benchmark
> before claiming otherwise.

  I will agree that it has come a long way, mostly hampered by having
to be crippled enough to still run DOS.  If it weren't for that, I
think they'd be running rings around bigger systems.  No, I haven't
tried a benchmark.  But it's a matter of architecture.  PCs just
simply weren't designed for it.  Recently there was a conversation in
comp.sys.dec where some fellow happened upon a MicroVAX III.  In
asking what it was, some guy explained that it offered about the same
performance as a 386DX/25.  Well, I've run both at work, and I have
both at home.  I can put 25 people on a MicroVAX III if it's properly
maintained.  I'd like to see someone try it with a 386DX/25.

  Out of curiosity...I honestly don't know much about the Pentium's
instruction set, beyond the obvious 8086isms.  What is ugly about it?

                           Regards,
                            -Dave McGuire
                             Operations

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From: Dave McGuire <[email-masked]>

On September 27, you wrote:
> Each Pentium is substantially more powerful than a 4/470 in every
> respect. As importantly, however, a 4/470 is a monsterously large
> machine compared to a Pentium and consumes far more power. I can stack
> ten PCI based Pentium PCs in a 19 inch rack. You may laugh at this
> consideration, but for those of us trying to run operations in places
> like New York City where every square foot can cost truly astronimical
> sums of money and where electricity is very expensive, this is a
> serious consideration. Replacing stupid obsolete 4/470s and 4/490s
> with stacks of far more powerful Sparcstations saved one client of
> mine with a high floor datacenter in a prime real estate location more
> than enough to pay for the conversion, and the machines were better,
> too.

  I'll try to do this in order:

  "Better in every respect" is flame bait that I will ignore.

  I agree completely on the space issue.  It's true that I can only
put three 4/400 systems in a 19" rack.  Actually, I *can* put several
more if I use 128mb RAM boards instead of lots of 32's, and only use
one SCSI host adapter...but then I'd worry about heat.

  "Stupid obsolete" is also flame bait that I will ignore.

  "Far more powerful" is true in some respects.  However, FOR OUR
APPLICATION, ( <-reread that) FOR OUR APPLICATION, Sparcstations, even
stuff like 10's, simply won't handle the users.  We have a major
competitor that tried it (two, actually) and it bit them on the butt.
Engineering workstations are simply not designed to replace big
multiuser systems.  It seems to me that you are trying to shoehorn and
retrofit hardware into applications for which it was not designed.  Is
there something good about this that I'm missing, or am I just being
anal-retentive about proper application for hardware?  Computer
manufacturers make workstations and they make servers.  They *really
are* different.

  About the "FOR OUR APPLICATION" stuff... I stress this because I
have no doubt that the stack of Sparcstations were better in *their*
application, but MY application here is the only one for which I can
speak of as having a great deal of experience with.  I would not
presume to debate you in *your* area of expertise.

                           Regards,
                            -Dave McGuire
                             Operations

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From: Dave McGuire <[email-masked]>

On September 27, you wrote:
> I don't think that it doesn't work. I've seen applications moved from
> 4/400 machines to 10's a lot and have never seen anything like what
> you are mentioning -- they've invariably sped up. This is what I would
> expect. As I said, the 10s have a faster bus, faster processors, more
> contexts, better controllers, and typically have faster
> disks.

  I agree that in many cases this will be true.  Our application,
specifically, is lots of people logged in reading mail, reading news,
ftp'ing files, downloading stuff, and stuff like that.  I mention it
because it may give you some insight as to what's going on here.

> However, I think this topic has wandered way away from what
> current is for, so I'm cutting myself off here.

  Agreed.

                            -Dave McGuire
                             Operations

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From: Dave McGuire <[email-masked]>

On September 27, you wrote:
> The comment reminds me of a manager I knew once who wouldn't believe
> that Sparcstation 10 pizza boxes were more powerful than his old
> fridge size sun 4/490 servers. After all, they were too small -- how
> could they be so powerful?  Before dismissing the idea as "silly", you
> ought to try it out.

  Mine is not an issue of size.  It's an issue of intended
application, even if it has been reduced to a `perceived' issue only.
I agree with your argument.  How many times do I have to ask you to
not let this conversation degenerate into a completely worthless flame
war?  Now that we have NetBSD to make it worthwhile, I may just "try
it out".

> The obvious 8086isms. Furthermore, the whole machine is dirty -- too
> much ten year old backward compatibility. You cannot, however, beat
> the price/performance.

  Well, if they're really under $2k for that kind of hardware, I think
I'd have to agree.

                            -Dave McGuire
                             Operations

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From: Dave McGuire <[email-masked]>

On September 27, you wrote:
> 1) Faster IO
> 2) Faster context switching
> 3) Faster processors

  Again, flame-bait ignored.

> Thats silly. If a 10 won't handle it, then a 4/400 series machine with
> far fewer contexts, a slower bus, slower processors and the like is
> certainly not going to handle it.

  Well, they do.  Wonderfully.  You sure seem to know more about
machine architecture than I do, so why don't you tell me why it works?

> > We have a major competitor that tried it (two, actually) and it bit
> > them on the butt.
> Probably bad engineering, not bad machines.

  I didn't say they were "bad machines"...I *love* 'em myself, I just
have this thing about using them for what they were designed to do.
Do you know the difference between a car and a truck, man?

  However, it *is* entirely possible that it was bad engineering.  My
company's competitors don't often invite me into their machine
rooms.. :)

> So what is the explanation you can give for why the old stuff is
> better for you?

  Again...You tell me.  It works.  Very well.  Much better than the
efforts of competitors trying to shoehorn it into desktop
workstations.  YOU TELL ME, man!  I'm open to your explanation!  If I
can go to my boss and tell him I have a solution that will shrink our
machine room down by a factor of ten, then I think I have a win and I
will buy you dinner.

                            -Dave McGuire
                             Operations

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From: [email-masked] (grantham)

> Do you know the difference between a car and a truck, man?

This isn't a very good analogy.

If my car has twice the engine power, twice the space in the trunk,
and twice the traction in the tires (not to mention that is was designed
from the beginning to be more comfortable) than your truck, the difference
is that my car will perform better than your truck, even though it has
a name befitting a smaller vehicle.

> workstations.  YOU TELL ME, man!  I'm open to your explanation!

I suspect it was bad engineering, on someone's part.  There is no
magic that will make up for

	1) better IO bandwidth
	2) better CPU power
	3) more memory
	4) better bus and logic design
	5) better software

no matter how much you guys flame back and forth.  In this case,
I'd have to suspect that the newer OS was at fault, probably
something having to do with context switching, virtual memory,
or configuration of some sort.  Maybe you had people running
multiple xtanks on the Sparc 10's?

As years pass, not only does speed/throughput per dollar grow, but the
rate of growth also increases.  A Pentium-90 PCI with a SCSI-2 adapter
and FDDI is a hell of a lot faster than the top-of-the-line 66MHz EISA
SCSI-2 16-bit Ethernet machine I bought last April, and the 66MHz machine
is now the internet server for dozens of undergraduate students at a
time, over ordinary ethernet.

I'm curious; what are you doing on these 4/???s?  Can you think
of any reason they would beat a Sparc 10?

		-Brad
-- 
Brad Grantham, [email-masked] >+------+< Happily slaved to NetBSD/Mac68k!
MacBSD : II, IIx, IIcx, IIci, SE/30, IIsi, IIvx -- The list is growing...

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From: Mike Miscevic <[email-masked]>

On Wed, 28 Sep 1994, John F. Woods wrote:

> This is getting way off topic, but I'd like to make a couple of observations,
> if for no other reason than to cheer up the owners of non-Intel systems :-).
> Running a big multi-user system isn't just a matter of CPU speed, unless
> all your users are doing nothing but using xv to look at JPEG images.
> Delivered disk bandwidth is a crucial part of *most* multi-user mixes,
> and that's something that expensive workstations have generally supplied
> much better than PCs have (and PCI or no PCI, I'll believe that a given
> PC has a *controller* that delivers better performance when I see a real
> benchmark run on it).
> 
> As an unusual example of this effect, when I brought up my NetBSD system
> full time, it was replacing an ancient CRDS Universe system, which contained
> a 12.5MHz 68020 central processor (and a 10MHz 68000 handling 12 serial
> ports).  According to dhrystone, the new system was approximately ten times
> the horsepower of the old system (and the memory system was at least four
> times the speed, too, another important thing that often gets lost in
> clock-size wars).  Yet as purchased, my 486/33 had great difficulty keeping
> up with the Universe system doing 38.4KB SLIP, and the Universe was still
> handling the modem at the time.  (There have been improvements in NetBSD's
> driver software since then, so *maybe* it would now be a fair match :-).

Different people define "fair" in different ways...

So *maybe* you should buy equivalent multi-serial port hardware for the
NetBSD system before you make such an observation. Maybe something that
wouldn't generate an interrupt for each byte that it received? Can we say
hardware buffer? Now that would be a fair match :)

> And, of course, if I had actually been using all twelve serial ports, it
> would have been quite difficult to have matched the capability of the 
> Universe.  (And if I had maxed out the Universe at 68 ports?)  Horsepower
> just isn't enough to make up for cripplingly braindamaged I/O design.
> 
> Fortunately for the PC side of this argument, the CRDS Versabus SCSI channel
> board was really slow, so my disk bandwidth improved quite a bit :-).  Though
> not by a factor of ten.
> 

--
Mike Miscevic         | net: [email-masked]  | Opinions expressed by
Rm 550, 160 Elgin St. | tel: (613) 781-4361       | me are not necessarily
Ottawa, Ont. K2P 2C4  | fax: (613) 238-7772       | those of my employer.

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From: [email-masked] (Rob Healey)

> hardware buffer? Now that would be a fair match :)
	But where is the smart card drivers, i.e. the ones that have
	a CPU offloading the interrupts? From a quick check it appears
	only the dumb cards that generate gobs of interrupts are
	supported by NetBSD at this time. i.e. no Digi, Computone and
	such type smart controllers. With those kinds of cards NetBSD
	would haul some serious levels of serial ass over the older 10MHz 68k
	serial controller!

		-Rob