On Wed, 9 Aug 2000, Glew, Andy wrote:
> Q: why is AFS so slow?
>
> E.g. if I am accessing files of, say, 100MB, and my local AFS
> cache is of 200MB, large enough to hold all of the AFS files
> I am accessing, and if I am the only person accessing these
> files... why is AFS still 16X slower than local disk?
>
Poorly tuned cache manager would be my first answer. Testing
that we have done between file access to local disk and access
of files already in the AFS cache (hot cache) does not support
your claim of 16X slower, the difference was not really noticeable
to the user. Now if your talking about comparing local disk access
to cold cache access then would numbers may be reasonable depending
on your network infrastructure and the cache manager configuration.
In any case I would look at cache manager tuning, there are so many
variables that effect cache performance, some of which you have no
control over (network latency, network bandwidth ...etc) it would
be hard to say which one has the most influence within your environment.
The process of cache manager tuning is one of trial and error.
What are your specifics of the AFS client you are measuring
type of client platform and configuration?
cache manager configuration (chunksize, dcache, stat, daemons)?
network latency and bandwidth from client to server?
network latency and bandwidth between AFS file server
and AFS data base server?
--
Terry McCoy email: [EMAIL PROTECTED]
Sr Systems Engineer phone: (219) 631-4274
Enterprise Systems Software
Office of Information Technologies
University of Notre Dame
