How would you handle 5000+ users?

[CAT-TALK Maint. Account]

In article <1990Nov6.014513.26144 at cims2.uucp> kew at cims2.uucp (Keith Walker) writes:
"What happens when you ask XENIX to handle 5000+ users in a passwd
"file? Is this the way to do things? All we want to do really is
"provide for e-mail between all of these users; but there's sooo many!
"I've never dealt with a system larger than about 100 users (and note
"that that is *users* not terminals -- there are only eight modems and
"a couple of terminals), and the thought of having to deal with over
"5000 users seems slightly intimidating.
"

We have almost 2000 users in the password file here at CAT-TALK and so
far there isn't a problem (ie: Xenix can handle it fine). For securities 
sake, keep an "authorized copy" of your password file offline and upload
it every now and then and compare it with the active password file to 
make sure no one has hacked into your system and added any bogus users.

"Does a stock XENIX or UNIX handle this kind of load well? Obviously,
"all those people aren't on-line at the same time, but is having a passwd
"file with 5000+ lines in it and 5000+ home directories just asking too
"much of humble XENIX?
"

We split the user's home directories between 4 separate filesystems.
Empty, all of these directories take 256000 bytes. The problem is that
we would run out of inodes if people started getting alot of files
in their directories. Also, spreading out the filesystems on 4
separate drives reduces that contention for access to any one disk drive,
keeping things from slowing down due to disk I/O.

Does anyone know if there *IS* a limit on number of entries in the 
password file? Does Xenix keep a "cache" in memory somewhere and if
so, is it a complete copy??