[OpenAFS] clarification on client caches

[Da Elf]

On Mon, 6 Sep 2004, Derrick J Brashear wrote:

=:Redirected to the list.
=:
=:On Mon, 6 Sep 2004, Wes Chow wrote:
=:
=:>
=:>>> Once afsd is started and
=:>>> assuming no cache resizes, does the number of V files that exist
=:>>> remain constant?
=:>>
=:>> Yes. And even if you resize the cache, it still does. File references are
=:>> established at afs startup. Making new ones later is "hard".

The Cache size is set in software before you start the Volume Server ...
inside bos.cfg


=:>
=:> Assuming no cache resizes, is there a maximum size for a V file and is
=:> it constant?  My understanding is that this maximum size is called the
=:> chunk size.  Is that correct?
=:
=:There is a maximum (chunk) size, yes, but it is not a hard limit on the
=:file size, it is enforced in software.


Yes, set up the VolSrv correctly. ALWAYS, ALWAYS, ALWAYS use at LEAST three
times the cache you think youre going to need.

=:> If the cache is resized, then does the chunk size also resize since
=:> the number of V files remains constant?
=:
=:No. Because remember, you have more V files than cache size/chunk size.
=:But yes, you can get into situations where you can't fill your cache.
=:
=:> Things work fine.  If I then run "fs setcachesize 30000000", accesses
=:> to /afs then proceed to hang.  I can change the cache size to about
=:> 25000000 and it still behaves properly.  The partition the cache is on
=:> is 60 gigs, so it's not running out of space.  Any ideas as to why
=:> it's hanging?

Yeah, try Div/1024 instead of Div/1k.  Drives are in 1024=1k and NOT
1000=1k.  The sooner folks realize that we do math in 1024, the happier
we're all going to be.

Memory cache works the same way.  Stop doing math in even numbers and
software works better for ya'.

=:This is basically the same question you asked before, right? I still have
=:no idea. Why not start with the cache size you want?
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