[OpenAFS] openafs performace problems

[Derrick Brashear]

On Tue, Jan 6, 2009 at 6:00 PM, Jason Edgecombe <jason@rampaginggeek.com> wrote:
> Rich Sudlow 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.
>
> Would enabling "fs storebehind" in AFS with a large value give a better
> comparison to NFS with caching?

No. attribute caching without coherency applies to reads also.

-- 
Derrick