Re: async vs. sync

["jehan.procaccia" <jehan.procaccia@int-evry.fr>]

Trond Myklebust wrote:

>ty den 16.11.2004 Klokka 08:15 (-0800) skreiv Lever, Charles:
>  
>
>>is the effect of the "sync" export option limited to NFSv3 COMMIT, or is
>>it limited to both NFSv3 COMMIT and NFSv3 FILE_SYNC/DATA_SYNC WRITE?
>>
>>what are the effects on NFSv4 writes and commits?
>>    
>>
>
>No! It is clearly not just limited to writes and commits.
>
>Look at the code in fs/nfs/vfs.c: there are EX_ISSYNC() exceptions that
>wrap calls to nfsd_sync_dir() in nfsd*_create(), nfsd_symlink(),
>nfsd_link(), nfsd_rename(), and nfsd_unlink().
>
>Cheers,
>  Trond
>
>  
>
By the way, I noticed on a performance factor of 30 (!) from an sync to 
async nfs v3 export FS :

sync export:

$time tar xvfz linux-2.6.8.tar.gz
real    64m18.618s
user    0m5.742s
sys     0m15.658s

async export:

$time tar xvfz linux-2.6.8.tar.gz
real    2m0.552s
user    0m5.838s
sys     0m15.678s


Is it really dangerous to use async ? why recent OS uses sync by default 
(My client is a Fedora Core 2 (kernel 2.6)  and server an RedHat 
Entreprise server 3 (kernel 2.4))

thanks.


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