[Gluster-users] Gluster vs NFS export sync

Santosh Pradhan spradhan at redhat.com
Fri Jul 11 10:40:46 UTC 2014

On 07/11/2014 02:37 PM, Franco Broi wrote:
> On Fri, 2014-07-11 at 14:22 +0530, Santosh Pradhan wrote:
>> On 07/11/2014 06:10 AM, Franco Broi wrote:
>>> Hi
>>> Is there any way to make Gluster emulate the behaviour of a NFS
>>> filesystem exported with the sync option? By that I mean is it possible
>>> to write a file from one client and guarantee that the data will be
>>> instantly available on close to all other clients?
>> I think FUSE also supports the sync option with mount similar to NFS.
> There's 2 types of NFS sync, server and client but they behave very
> differently. With sync at the client end, NFS just calls fsync on close
> (I think),

No. If the NFS client is mounted with sync flag i.e. -o sync, then all 
the WRITEs will be synchronous i.e. they wont be cached in client side 
and they(WRITEs) will hit the server with FILE_SYNC (stable write) flag 
which is nothing but FILE I/O with O_SYNC flag.

> with sync at the server end, all writes are synchronous.
> Opening the file with O_SYNC also doesn't give the desired effect
> although you'd think it would.
It should be same as above.

>   NFS must have some way of communicating
> the file attribute changes to all the clients immediately the write
> completes.
>> Man page snippet for fuse(8):
>>          Most of the generic mount options described in mount are
>> supported (ro, rw, suid, nosuid, dev,
>>          nodev, exec, noexec, atime, noatime, sync, async, dirsync).
>> Filesystems are mounted  with
>>          nodev,nosuid by default, which can only be overridden by a
>> privileged user.
>> Thanks,
>> Santosh
>>> Cheers,
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>>> Gluster-users at gluster.org
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