[OpenAFS] openafs performace problems

Rich Sudlow rich@nd.edu
Tue, 06 Jan 2009 17:04:08 -0500

Mattias Pantzare wrote:
> On Tue, Jan 6, 2009 at 20:45, Rich Sudlow <rich@nd.edu> wrote:
>> 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.
> If your existing application is working fine on NFS with attribute
> caching you should _not_ turn it off when you are comparing to AFS.
> The application can clearly work with the attribute cache. (The
> attribute cache is normally not a problem)
> In fact the test would be misleading if you did turn the cache off.

That's correct and then you're comparing apples and oranges.

Rich Sudlow
University of Notre Dame
Center for Research Computing
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