Ok, first i'd like to publicly state that I'm speaking partly out my butt here;
that is, I haven't researched this as thoroughly as I'd like, so please keep in
mind that I'm mostly speaking from experience :-).
> 1. Any good advice on how to best determine the size of
> /usr/vice/cache?
"black magic"
I don't think there's any simple formula. Personally I think it depends on:
a) how much disk space the machine has
b) how fast the machine is
c) what you're running on the machine
d) how many people are using the machine
e) what experimenting tells you
Hint #1: Disk space is cheap. Don't let "a" be a true factor :-), go get more
space if you need it.
Example 1:
2 CPU Alpha 2100 4/275
used as multi-user system (generic "user system")
around 8G local disk space
Up to 30+ users at one time on system
Current vice cache: 800M
Currently, only 680M is being used, but people do move huge datasets around
this system from time to time. We tried more, we tried less. 800M is what we
settled on.
Hint #2: Vice cache (er, AFS cache, sorry :-) is like swap space: Too much and
your system may spend too much time trying to find files, too little and it
spends too much time moving things in and out of the cache.
Example 2:
8(?) CPU SGI Power Challenge
used as multi-user heavy-duty number cruncher
around 130G of local disk space
Up to 10+ users at one time, plus non-interactive crunching processes
Current vice cache: 300M
Most crunching users crunch locally so extra huge amounts of vice cache hasn't
been needed.
Example 3:
1 CPU DECstation 5000/240
used as news server running pmax_netbsd
(stop laughing)
around 15G local disk space
Primary use for non-interactive inn/nnrp processes (~25 at it's busiest)
Current vice cache: 20M
The only AFS interaction this system gets is for "software updates" (except INN
:-) which are done via the CMU "depot" package, over AFS. 20M is more than
enough for that.
Hint #3: Don't be afraid to change your cache size up and down until you find
what you need, as you can almost always do it on the fly. "fs setca" will set
a new size temporarily & if it works you can set it permanantly. However, I
would recommend a few days between each change, unless it's painfully obvious
you have a major problem. I say this for two reasons: vice caches do become
corrupted from time to time & I'm not sure if playing with the sizing might
tickle that, and you will likely need a few days (maybe weeks) to determine if
your sizing is what you need.
Hope that all helps.
> 2. We have users who will be loading libraries up to one gig. The
> question is
> does a copy of the whole file sit in the cache?
That's a good question & one I don't yet know the answer to. I know we had a
user moving 500M+ datasets into AFS - on a [*cough*] Decstation 5000/240
(multiuser!) with little disk space & about a 180M vice cache. It was _ugly_,
the machine would get very very slow.
I'd like to look more into this but perhaps someone else on this list knows
(far :-) more about cache management details than I.
e.
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[EMAIL PROTECTED] Esther Filderman [EMAIL PROTECTED]
Senior System Mangler, News & AFS Dominatrix
Pittsburgh Supercomputing Center
