[CentOS] OT: Caching synchronous writes

[Ross Walker]

On Apr 24, 2010, at 4:53 PM, Les Mikesell <lesmikesell at gmail.com> wrote:

> Ross Walker wrote:
>> On Apr 24, 2010, at 4:34 PM, Les Mikesell <lesmikesell at gmail.com>  
>> wrote:
>>
>>> Ross Walker wrote:
>>>> On Apr 24, 2010, at 12:43 PM, Les Mikesell <lesmikesell at gmail.com>
>>>> wrote:
>>>>
>>>>> Ross Walker wrote:
>>>>>> NFS should always be 'sync' if performance isn't good, then your
>>>>>> storage isn't good.
>>>>> Why demand sync on remote storage when you typically don't have it
>>>>> locally?
>>>>> Programs that need transactional integrity should know when to  
>>>>> fsync
>>>>> () and for
>>>>> anything else there's not much difference whether you crash before
>>>>> or after a
>>>>> write() was issued in terms of it not completing.
>>>> Yes, but 'async' ignores those fsyncs and returns immediately.
>>> That sounds like a bug in the nfs client code if fsync() doesn't
>>> block until all
>>> of the data is committed to disk.
>>
>> It's not the client side I'm talking about, but the server side. We
>> were talking NFS servers and exporting sync (obey fsyncs) vs async
>> (ignore fsyncs).
>>
>> The client always mounts async, that's not the problem.
>
> That's different.  I thought the nfs spec was always sync on the  
> server side and
> the client says when async is OK.  And there's some special case  
> response to
> handle the case where the server rebooted between the async writes  
> and the
> subsequent fsync().

All the NFS info you wanted, but were afraid to ask:

http://nfs.sourceforge.net/

-Ross