[OpenAFS-devel] tweaking openafs configuration - chunksize, cache expiration and cache renewal

[Jason Edgecombe]

Stephan Zimmer wrote:
> Hi guys,
> this is my very first post to this mailing list and I hope that someone
> following the list could point me to a solution for this bunch of
> questions I am going to ask in this email.
>
> We are trying to utilize AFS in order to avoid the installation of local
> software on our machine by sourcing precompiled versions from a
> different cell. As the cell we are fetching our data from is located
> 1000 km away from us we are experiencing serious latency issues although
> our cache of currently 50 GB should give us plenty opportunities to
> cache whatever we need.
>
> Tests showed in fact that sub sequential exercising of the same tasks is
> not as performant as we would have expected it: after having run it for
> the first time I would have thought that the second call (from a
> different user though) should entirely rely on the cached content the
> first user had created during his call. However, it appears as the cache
> content expires very soon after having accessed it for the first time.
>
> For our particular setup we were thinking of setting up our machine to
> cache entire parts of the cell we were taking our stuff from and do this
> caching via a cron job. This apparent expiration appears to be a major
> drawback but after having read a bunch of references I couldn't figure
> out what to change in our configuration.
>
> The other issues is whether it is advised to change the chunksize as
> this would reduce the chunks that are used for a generic file transfer.
> Is it recommended to change this parameter - does it bring much
> performance?
>
> Lastly, how do you guys think about the general plan - setting up an
> afs-configuration that caches entire afs volumes from a designated cell
> once a day or something... is this really practically or rather not
> recommended due to performance issues?
>
> Any help would be highly valued,
> thank you very much,
> cheers,
> Stephan Zimmer
>   
Could you have a local fileserver from the remote cell and have 
read-only relicas there?

Jason