[Linux-cluster] Samba Statefull Failover

Wed Jun 23 20:11:51 UTC 2010

Jason,

You're correct.  Sorry.  I'm a protocol geek, and I was addressing the
protocol issues.

Samba 3 has SMB2 in the development tree, but not yet released as stable.
It should be pretty close to a testing release, however, so folks interested
in testing SMB2 support should watch the samba-technical list.

If you are running any pre-Vista Windows products, then you are also correct
that SMB2 won't be supported on those.

Having said all of that...  The problem is that the Windows SMB1 clients
have no mechanism for recovering if the TCP connection is lost.  If they are
using OpLocks, for instance, all cached updates are lost if the connection
goes down.  The clients simply throw away state and start over.  If the
applications running on those clients do not know how to re-establish the
correct state then they will lose data.

This has nothing to do with CTDB, since it all happens on the client side.

SMB2, however, has what are called "persistent file handles".  The Windows
SMB2 client can maintain state even if the TCP connection fails.  When the
connection is re-established, the client can resynchronize with the server
and all is well.

Chris -)-----

Jason Fitzpatrick wrote:
> Hi Chris..
> 
>>From reading  up on the SMB2 protocol it seems that this is
> implemented within Vista and greater MS clients, but I do not seem to
> be able to track support for SMB2 within SAMBA
> 
> I see that there is a Samba4AD project but cannot find rpms for RHEL
> and am a bit cagey about putting a dev version onto a critical file
> server.
> 
> And the Citrix (client) servers are 2003 SMBv1 anyway so that kind of
> kills that anyway.
> 
> Thanks
> 
> Jay
> 
> On 22 June 2010 17:08, Christopher R. Hertel <crh at ubiqx.mn.org> wrote:
>> Please note that the SMB/CIFS protocol itself does not gracefully recover
>> from a failover.  SMB2 is much better in this regard.  This is a client-side
>> problem due to limitations in the protocol and client expectations.
>>
>> Chris -)-----
>>
>> Frank de Groodt wrote:
>>> Make sure you use virtual public ip addresses managed by CTDB, not the ones bound to your NICS.
>>>
>>> Frank.
>>> ________________________________________
>>> From: linux-cluster-bounces at redhat.com [linux-cluster-bounces at redhat.com] On Behalf Of Abhijith Das [adas at redhat.com]
>>> Sent: Tuesday, June 22, 2010 4:33 PM
>>> To: linux clustering
>>> Cc: Sumit Bose; Gunther Deschner; Simo Sorce
>>> Subject: Re: [Linux-cluster] Samba Statefull Failover
>>>
>>> ----- "Jason Fitzpatrick" <jayfitzpatrick at gmail.com> wrote:
>>>
>>>> From: "Jason Fitzpatrick" <jayfitzpatrick at gmail.com>
>>>> To: linux-cluster at redhat.com
>>>> Sent: Tuesday, June 22, 2010 6:43:36 AM GMT -06:00 US/Canada Central
>>>> Subject: [Linux-cluster] Samba Statefull Failover
>>>>
>>>> Hi all
>>>>
>>>> Just wondering if it is possible to statefully migrate smb
>>>> connections
>>>> between cluster nodes, I am running ctdb (Samba's Cluster software)
>>>> but all connections are dropped when the service is failed between
>>>> nodes
>>>>
>>>> Setup is as follows
>>>>
>>>> 2 node cluster
>>>> DRBD backend shared storage in Master Master configuration
>>>> cman presenting GFS2 /Storage folder
>>>> Samba + Winbind + CTDB used to present /Storage/Test_Share via
>>>> \\clustername\test_share (both nodes are AD integrated)
>>>>
>>>> Connections to replicated storage are working fine, AD accounts are
>>>> authenticated correcly and smbstatus shows that CTDB is load
>>>> ballancing the cluster address between nodes correctly,
>>>>
>>>> When I run ctdb shutdown I expect existing connections to be migrated
>>> Also, I think "ctdb shutdown" is not the right command (Use "ctdb disable", it
>>> should all be in the man pages). Only one node should fail so that the
>>> other node can take over the IP address. If the IP address is not taken
>>> over, the clients will probably not be able to reconnect.
>>>
>>> Cheers!
>>> --Abhi
>>>
>>> --
>>> Linux-cluster mailing list
>>> Linux-cluster at redhat.com
>>> https://www.redhat.com/mailman/listinfo/linux-cluster
>>>
>>> --
>>> Linux-cluster mailing list
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>> --
>> "Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
>> Samba Team -- http://www.samba.org/     -)-----   Christopher R. Hertel
>> jCIFS Team -- http://jcifs.samba.org/   -)-----   ubiqx development, uninq.
>> ubiqx Team -- http://www.ubiqx.org/     -)-----   crh at ubiqx.mn.org
>> OnLineBook -- http://ubiqx.org/cifs/    -)-----   crh at ubiqx.org
>>
>> --
>> Linux-cluster mailing list
>> Linux-cluster at redhat.com
>> https://www.redhat.com/mailman/listinfo/linux-cluster
>>
> 
> 
> 

-- 
"Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
Samba Team -- http://www.samba.org/     -)-----   Christopher R. Hertel
jCIFS Team -- http://jcifs.samba.org/   -)-----   ubiqx development, uninq.
ubiqx Team -- http://www.ubiqx.org/     -)-----   crh at ubiqx.mn.org
OnLineBook -- http://ubiqx.org/cifs/    -)-----   crh at ubiqx.org