does the linux NFS client support for failover to a replica share (read-only share)

does the linux NFS client support for failover to a replica share (read-only share)

[sebastien cabaniols]

Hello linux-nfs mailing list.

I would like to know if the linux nfs client included in current
versions of the kernel supports fail-over to a replica on another nfs
server, I am using (manually) synchronized read-only shares...

I found very few information on Google about this topic and I suspect
this is not implemented.

I actually tried to setup this using SLES12SP1 (3.12.49 kernel) but I
failed so far. I am not attached to this distribution/version in
particular, just trying to see it working for real.

( I did some "rpcdebug -m nfs" session and it seems the fs_locations
is not getting properly populated on my setup )

Any confirmation this should work or not would actually help me.

THX.


note from the exports man page:

       replicas=path@host[+host][:path@host[+host]]
              If  the  client  asks for alternative locations for the
export point, it will be given this list of alternatives.
              (Note that actual replication of the filesystem must be
handled elsewhere.)

Re: does the linux NFS client support for failover to a replica share (read-only share)

[J. Bruce Fields]

On Tue, Jun 07, 2016 at 10:02:19PM +0200, sebastien cabaniols wrote:
> Hello linux-nfs mailing list.
> 
> I would like to know if the linux nfs client included in current
> versions of the kernel supports fail-over to a replica on another nfs
> server, I am using (manually) synchronized read-only shares...
> 
> I found very few information on Google about this topic and I suspect
> this is not implemented.

That's correct (unless I've missed something!).

> I actually tried to setup this using SLES12SP1 (3.12.49 kernel) but I
> failed so far. I am not attached to this distribution/version in
> particular, just trying to see it working for real.
> 
> ( I did some "rpcdebug -m nfs" session and it seems the fs_locations
> is not getting properly populated on my setup )
> 
> Any confirmation this should work or not would actually help me.
> 
> THX.
> 
> 
> note from the exports man page:
> 
>        replicas=path@host[+host][:path@host[+host]]
>               If  the  client  asks for alternative locations for the
> export point, it will be given this list of alternatives.
>               (Note that actual replication of the filesystem must be
> handled elsewhere.)

Yes, the server side (assuming you've got the backend replication
working) is pretty easy, and should work (though I don't know if it's
gotten any testing).  The client has the harder job here.

--b.

Re: does the linux NFS client support for failover to a replica share (read-only share)

[Malahal Naineni]

J. Bruce Fields [bfields@fieldses.org] wrote:
> On Tue, Jun 07, 2016 at 10:02:19PM +0200, sebastien cabaniols wrote:
> > Hello linux-nfs mailing list.
> > 
> > I would like to know if the linux nfs client included in current
> > versions of the kernel supports fail-over to a replica on another nfs
> > server, I am using (manually) synchronized read-only shares...
> > 
> > I found very few information on Google about this topic and I suspect
> > this is not implemented.
> 
> That's correct (unless I've missed something!).
> 
> > I actually tried to setup this using SLES12SP1 (3.12.49 kernel) but I
> > failed so far. I am not attached to this distribution/version in
> > particular, just trying to see it working for real.
> > 
> > ( I did some "rpcdebug -m nfs" session and it seems the fs_locations
> > is not getting properly populated on my setup )
> > 
> > Any confirmation this should work or not would actually help me.
> > 
> > THX.
> > 
> > 
> > note from the exports man page:
> > 
> >        replicas=path@host[+host][:path@host[+host]]
> >               If  the  client  asks for alternative locations for the
> > export point, it will be given this list of alternatives.
> >               (Note that actual replication of the filesystem must be
> > handled elsewhere.)
> 
> Yes, the server side (assuming you've got the backend replication
> working) is pretty easy, and should work (though I don't know if it's
> gotten any testing).

Bruce, we did test the server side couple years ago. I don't remember
any issues on the server side. We did some rudimentary support on the
client side (we were using rsync for replication and our exports were
read-only!). I remember "find" having an issue with inode number change
while it was running, but don't remember any other issues. The client
patches never made it to mainline though.

Regards, Malahal.

Re: does the linux NFS client support for failover to a replica share (read-only share)

[J. Bruce Fields]

On Mon, Jun 13, 2016 at 07:10:56PM -0500, Malahal Naineni wrote:
> J. Bruce Fields [bfields@fieldses.org] wrote:
> > On Tue, Jun 07, 2016 at 10:02:19PM +0200, sebastien cabaniols wrote:
> > > Hello linux-nfs mailing list.
> > > 
> > > I would like to know if the linux nfs client included in current
> > > versions of the kernel supports fail-over to a replica on another nfs
> > > server, I am using (manually) synchronized read-only shares...
> > > 
> > > I found very few information on Google about this topic and I suspect
> > > this is not implemented.
> > 
> > That's correct (unless I've missed something!).
> > 
> > > I actually tried to setup this using SLES12SP1 (3.12.49 kernel) but I
> > > failed so far. I am not attached to this distribution/version in
> > > particular, just trying to see it working for real.
> > > 
> > > ( I did some "rpcdebug -m nfs" session and it seems the fs_locations
> > > is not getting properly populated on my setup )
> > > 
> > > Any confirmation this should work or not would actually help me.
> > > 
> > > THX.
> > > 
> > > 
> > > note from the exports man page:
> > > 
> > >        replicas=path@host[+host][:path@host[+host]]
> > >               If  the  client  asks for alternative locations for the
> > > export point, it will be given this list of alternatives.
> > >               (Note that actual replication of the filesystem must be
> > > handled elsewhere.)
> > 
> > Yes, the server side (assuming you've got the backend replication
> > working) is pretty easy, and should work (though I don't know if it's
> > gotten any testing).
> 
> Bruce, we did test the server side couple years ago. I don't remember
> any issues on the server side. We did some rudimentary support on the
> client side (we were using rsync for replication and our exports were
> read-only!). I remember "find" having an issue with inode number change
> while it was running, but don't remember any other issues. The client
> patches never made it to mainline though.

Oh, thanks for the reminder.

I wonder if the client's closer to ready for failover support now.  I
don't remember what the issues were.

--b.

Re: does the linux NFS client support for failover to a replica share (read-only share)

[sebastien cabaniols]

If the patch/git commit is somewhere, I can give it a go... for
failing over to a different server without shared storage I replicate
using dd so that the same inodes get served. I am really interested to
see the client failover to another IP address alone.

2016-06-14 16:57 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>:
> On Mon, Jun 13, 2016 at 07:10:56PM -0500, Malahal Naineni wrote:
>> J. Bruce Fields [bfields@fieldses.org] wrote:
>> > On Tue, Jun 07, 2016 at 10:02:19PM +0200, sebastien cabaniols wrote:
>> > > Hello linux-nfs mailing list.
>> > >
>> > > I would like to know if the linux nfs client included in current
>> > > versions of the kernel supports fail-over to a replica on another nfs
>> > > server, I am using (manually) synchronized read-only shares...
>> > >
>> > > I found very few information on Google about this topic and I suspect
>> > > this is not implemented.
>> >
>> > That's correct (unless I've missed something!).
>> >
>> > > I actually tried to setup this using SLES12SP1 (3.12.49 kernel) but I
>> > > failed so far. I am not attached to this distribution/version in
>> > > particular, just trying to see it working for real.
>> > >
>> > > ( I did some "rpcdebug -m nfs" session and it seems the fs_locations
>> > > is not getting properly populated on my setup )
>> > >
>> > > Any confirmation this should work or not would actually help me.
>> > >
>> > > THX.
>> > >
>> > >
>> > > note from the exports man page:
>> > >
>> > >        replicas=path@host[+host][:path@host[+host]]
>> > >               If  the  client  asks for alternative locations for the
>> > > export point, it will be given this list of alternatives.
>> > >               (Note that actual replication of the filesystem must be
>> > > handled elsewhere.)
>> >
>> > Yes, the server side (assuming you've got the backend replication
>> > working) is pretty easy, and should work (though I don't know if it's
>> > gotten any testing).
>>
>> Bruce, we did test the server side couple years ago. I don't remember
>> any issues on the server side. We did some rudimentary support on the
>> client side (we were using rsync for replication and our exports were
>> read-only!). I remember "find" having an issue with inode number change
>> while it was running, but don't remember any other issues. The client
>> patches never made it to mainline though.
>
> Oh, thanks for the reminder.
>
> I wonder if the client's closer to ready for failover support now.  I
> don't remember what the issues were.
>
> --b.



-- 
et où qu'y va en vacances Nicolas Hulot ?