[Samba] status of Continuous availability in SMB3

Michael Adam obnox at samba.org
Wed Aug 31 08:29:51 UTC 2016

On 2016-08-31 at 08:13 +0000, zhengbin.08747 at h3c.com wrote:
> hi Michael Adam:
> Thanks for you work on samba. Here I am looking for some advice and your help.
> I have been stuck in continuous availability of samba 4.3.9 for two weeks. Continuous availability in SMB3 is an attractive feature and I am strugling to enable it.
> smb.conf, ctdb.conf are attached. Cluster file system is cephfs and mount to /CephStorage
> client: Windows 8 Pro
> root at node0:~# samba --version
> Version 4.3.9-Ubuntu
> root at node0:~# ctdb version
> CTDB version: 2.5.1
> root at node0:~# ctdb status
> Number of nodes:3
> pnn:0    OK (THIS NODE)
> pnn:1    OK
> pnn:2    OK
> Generation:1131631460
> Size:3
> hash:0 lmaster:0
> hash:1 lmaster:1
> hash:2 lmaster:2
> Recovery mode:NORMAL (0)
> Recovery master:0
> root at node0:~# ctdb ip
> Public IPs on node 0
> 0
> My test procedure is as below.
> 1. The virtual IP is holded by onde0( Client(Win 8) accesses \\\<file:///\\\>. Copy a large file out of the remote dir and make sure the operation taking a period of time.
> 2. Restart the ctdb process on node0 to force virtual IP to be taken over by node1(
> 3. At the moment the virtual IP is taken by node1, the copy operation is interrupted simultaneously and can not continue the operation without re-copy the whole file.
> When carring out the test, I have a wireshark process run. It is confirmed that protocol smb3 is used. In the tree connection phase, server's response to client claims that it does not support DFS/Continuous Availability.
> I'm confused that does SMB3 protocol in samba 4.3.9 just been partly implemented and CA is of one the feature unspported by this version of samba. Or I have not found the way to enable the CA feature. Look forward to your kind advice.

It is true that to date, CA is not implemented in Samba.
The SMB2 and SMB3 protocols have a number of capabilities
that are optional in the sense that the server tells the
client whether it supports them or not.

Among those are:
- persistent handles (corresponding to the share capability CA)
- multi-channel
- leases
- directory leases
- encryption
- large MTU

Of these, samba currently supports leases, encryption,
and large MTU. multi-channel support is experimental.
persistent handles are being worked on.

Hope this helps,

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