Memory impact on performance of Sun3

[Tim Ehrhart]

>Chuck Howell <howell at mitre.arpa> writes:
>At what point does adding memory to a Sun3/75 reach the point of
>sharply diminishing returns?  We have fast disks on our file servers
>(Eagles), and four meg on our 3/75's.  It seems pretty clear that swapping
>is sharply reduced in going from two meg to four; is there much gained
>by going to eight, or even sixteen?  What about servers?  Is there
>much to be gained by beefing up server memory to eight or sixteen meg?

My personal experience with Sun-2's running 2.x or 3.x or Sun-3's running 3.x
on various file server configuration have shown me that they (file servers)
are not memory bound. Our file servers usually don't even have Sun consoles
on them so they never run suntools. That makes a tremendous difference to
file server performance. For the rest, a file server typically runs a much
smaller subset of programs (i.e. nfs stuff, network daemons) than a normal
client (i.e. editors, graphix, databases, AI development). We also discourage
"logging-in" to the file server to minimize character based I/O interrupt
handling. Why not ? Everything is accessible over NFS.

Don't have much experience with 8MB Sun-3/75 as diskless clients. Just got
one, but I recommend throwing memory at clients instead for file servers.

Take a good look at your file server using vmstat and you'll be suprised.
Here's how we configure 'em:

Hardware		OS		MB  	# clients 	Disks
Sun-2/170		2.3		2		~12-17		451, 2 Eagles (~760 MB)
Sun-3/180		3.0		4		~10-12		451, 2 Super Eagles (~1.1 GB)

Tim Ehrhart, SRI International, Menlo Park, CA 	94025