Server Capacity Update

[Allan Kobelansky]

Here is a compendium of replies I received from readers regarding the
following scenario I proposed:

> Consider the following scenario:
> 
> Server: Sun 3/280 with 32 Mbytes of core
>         2 800 Mb Disks (possibly 3)
> 	Qty: 1
> 
> Workstations: Sun 3/60 with 8Mb of core
> 	      Diskless
> 	      Qty: 26 - 30
> 
> Is such a configuration possible?

*** Reply from smiller at umn-cs.cs.umn.edu (Steve Miller):

Yes.   You will gain some performance if you maintain your 15 workstation
level, but if you increase the number of workstations you won't see much
of an increase.   Adding a second ethernet controller will help some, but
the second ethernet controller (on Sun's anyhow) has signifcantly slower
throughput than the first.  

You won't overload the ethernet.  With only one server and 15 clients per
subnet the ethernet will be loafing along.     

To get maximum performance make sure you have a fast disk controller -
Sun's new controller or a ciprico will do the trick.

Pray that Sun or someone gets a decent ethernet controller on the market
for Sun fileservers.    

You will probably also do better if you install the 4.3bsd tcp code into
your kernels.

*** Reply from krempel at pacrat.npac.syr.edu (Henry B.J. Krempel):

I'd be interested in hearing whether that would work.  You must be using
some other machine as your Ethernet gateway to the outside world?

*** Reply from davem at gonzo.eta.com (Dave Marquardt):

We have 4 3/280's, one 4/280, and about 60-80 Sun-3/50s and Sun-3/60s on
our Ethernet, and it's very overloaded!  We're going to switch to having
no more than one server and 20 clients per subnet, "Real Soon Now", our
system/network administrator says.

*** Reply from mr at ritd.co.uk, uunet!ukc!ritd!mr, sunuk!brains!mr (Martin Reed):

Well, my normal response to hanging ~30 clients of a single server would
be "forget it!". However, I guess times may be a changing.

You at least have the decency to put 8Mb in each and 32Mb in the server.
Now if the clients aren't doing very much to cause paging (large programs
*or* starting lots of smaller ones) then you may get away with it.
Certainly put a decent (not 451) disk controller in the server if you
haven't already, and don't put more than 2 disks per controller. Note the
"normal" magic numbers are 8-12 diskless clients per server.

Making the clients "dataless" is in interesting step. This means that they
have local disk for /, /usr and swap. I am aware of a number of people who
have measured such networks and I understand that numbers like 25 or even
50 clients per server are in with a chance. Of course, this is still all
very work-load dependent. Mind you, has potential management problems
trying to keep all those local "system" disks in sync (mounting stuff
read-only as in 4.0 helps a lot).

In either approach, think about making the server a 4/280; you might
benefit from the extra oomph.

I would be surprised if it was worth splitting the Ethernet - if the wire
is going to try and handle that much traffic then I believe that a single
server would already be on its knees.

I'm slightly surprised that you think that you can live on "only" 2-3
800Mb drives for that large a community, but I guess you have played with
the numbers :-).

I assume that you have tried bouncing your ideas of someone in Sun Tech
Support? Might take a few tries to find someone willing to say useful
things.

Summary: diskless - probably not; dataless - good chance of working.
Caveat: depends a lot on your work-load.

- - - - - - - - -

Thanks to all who replied. We are evaluating these comments and as soon as
we have decided what route will be pursued I will post.

Allan Kobelansky - Bell Northern Research, Montreal, Quebec.

bnrmtl!kobelan at larry.mcrcim.mcgill.edu
-or-
mcgill-vision!bnrmtl!kobelan