[OpenAFS] openafs performace problems

Rich Sudlow rich@nd.edu
Tue, 06 Jan 2009 14:45:19 -0500

Mattias Pantzare wrote:
> On Tue, Jan 6, 2009 at 17:10, Rich Sudlow <rich@nd.edu> wrote:
>> Esther Filderman wrote:
>>> To some degree, OpenAFS will always write slower than standard NFS,
>>> because AFS is actually making sure it's not writing crap.  NFS will
>>> happily write stuff at blazingly fast speeds, not caring whether the
>>> data it writes is sane or corrupted.
>> The reason NFS appears to be faster is because you're not doing an
>> apple - apples comparision - if you were you would have to turn off
>> attribute caching on NFS - at that point you'd find that performance
>> is essentially equal
> Why would you turn off attribute caching? That is a part of NFS.

You're correct you generally wouldn't - But if you are truly comparing
NFS and OpenAFS you would need to.

> Why would attribute caching make the test be an apples - oranges comparison?

Because you have no cache coherancy on NFS to verify that data is 
propogated out and seen simultaneously on multiple clients
(V2 & 3)  whereas with OpenAFS that cache coherancy is there.


Rich Sudlow
University of Notre Dame
Center for Research Computing
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