[OpenAFS] openafs performace problems

Mattias Pantzare pantzer@ludd.ltu.se
Tue, 6 Jan 2009 22:58:45 +0100

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.