[OpenAFS] cache managers on openAFS clients NOT caching

Derek Atkins warlord@MIT.EDU
Wed, 29 Sep 2004 14:12:14 -0400

Please be sure to CC openafs-info on all replies.

One way to test whether the cache is caching or not is to start AFS
with NO cache and compare it to starting AFS with a primed cache.  You
can clear the cache by "rm /usr/vice/cache/*Items" (make absolutely
sure that AFS is NOT running when you execute this command).  Then
when you start AFS it will have no cache.  I bet it takes much longer
to execute your program with an empty cache than it does with the
primed cache.


Kristian <kristian@hitech-sanita.it> writes:

> Hi,
> I did expect stat information to be looked up every time. I am sure
> inode data has not been changed because the executable I am testing on
> is in a read-only replicated volume which has not been modified... not
> even its rw counterpart.
> I would expect volume/stat information not to generate much network
> traffic and to be fetched very quickly. I have used afsmonitor to keep
> an eye on the number of fetches and a network grapher to see the amount
> of traffic generated: the number of fetches increases rapidly by about
> 100 (don't have the exact figure right now) and the amount of traffic
> shown by the grapher is equivalent to the first ever run of the
> executable. 
> I understand this is not a very accurate way of analysing performance
> and AFS expected behavior. Is there a better way to achieve this? I have
> configured a squid web proxy server once and its access log file is
> exactly what I would be looking for: simple messages like
> 	TCP_HIT	: for file in cache
> 	TCP_MISS: for file NOT in cache
> Anyway... I thought that it might be a clock synchronization issue... my
> clocks weren't perfectly sync'd. After fixing that it is still behaving
> like this.
> Il mer, 2004-09-29 alle 17:52, Derek Atkins ha scritto:
>> Hi,
>> The stat cache is not stored on disk, so it will always go back
>> to the server for stat information after a reboot.  However if the
>> inode data has not changed it should not need to refetch the data
>> across a reboot.  Are you sure you're seeing data re-fetch and not
>> just volume/stat information?
>> -derek
>> Kristian <kristian@hitech-sanita.it> writes:
>> > Hi There,
>> >
>> > I have set up an AFS server and everything works correctly. Clients
>> > running the cache manager can connect and correctly access files for
>> > which users have been authorized.
>> >
>> > However, on client reboot, and thus on cache manager restart, it seems
>> > that the cache stored on disk is not being used at all. Basically, when
>> > I execute a binary stored in my AFS cell it gets copied into my local
>> > disk cache, but after reboot, even though the cache manager startup
>> > script says that some files in my local disk cache are "not empty", I
>> > can tell that it is still fetching the very same executable from the
>> > only AFS database machine. Is there anything in particular I should be
>> > looking at?
> -- 
> Kristian <kristian@hitech-sanita.it>
> Hi.Tech srl

       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord@MIT.EDU                        PGP key available