O_SYNC behavior?

[Matthias Schniedermeyer]

On 27.04.2010 09:25, Nathan Scott wrote:
> 
> ----- "Ray Van Dolson" <rvandolson at esri.com> wrote:
> 
> > End-user question:
> > 
> > NFS client accessing an NFS export on an XFS based filesystem via
> > "sync" (O_SYNC) mode.
> > 
> > Will write confirmation be sent back from the NFS server when the
> > data is written to the xfs journal,
> 
> Data is never written to the journal.

I don't think that answers the intented question.

I guess the correct answer is:
It depends on the server-side configuration.
An "async" export gets the "done"-answer immediatly.
An "sync" export (only when also mounted "sync" AFAIU) waits at least 
until the write command is send down the stack, maybe even until the 
data actually hit the platters or silicon in the SSD-case.

man 5 exports:
- snip -
sync:	Reply to requests only after the changes have been committed to stable storage
- snip -

But i guess the performance will be horrible when both side are "sync".




Bis denn

-- 
Real Programmers consider "what you see is what you get" to be just as 
bad a concept in Text Editors as it is in women. No, the Real Programmer
wants a "you asked for it, you got it" text editor -- complicated, 
cryptic, powerful, unforgiving, dangerous.