Re: [Nbd] how does NBD handle disconnections?

[Francis Giraldeau <francis.giraldeau@...132...>]

Wouter Verhelst a écrit :
> On Mon, Jul 30, 2007 at 10:28:58PM -0400, Francis Giraldeau wrote:
>   
>> Hi,
>>
>> I would like to use the -persist option of NBD. I thought that using
>> this option would make nbd-client reconnect if the corresponding
>> nbd-server is killed, but it didn't.
>>     
>
> Never the less, that is the behaviour that nbd-client tries to achieve.
>
> How is it failing? Could you provide a bit more detail?
>
>   
As you may know, LTSP is using NBD to replace NFS root. I'm concerned
about high availability. It was easy to setup high available NFS server
with heartbeat. The problem with NBD is that one process is started for
each connexion on one server. If a failover occur, the client must start
a new process on the other server. The client should tolerate a
disconnection and create a new one until it succeed.

Another example, if the LTSP server reboots, then you need to reboot all
the thin-clients, that may even not respond anymore. The nbd-client
should handle this.

Since the NBD device is read only, so it should be easy to do it.

I saw also that nbd-server process are sometime left behind and never
terminate. Should look to that also.

The nbd-monitor could be a solution. Does work is done to it?

Thanks a lot for all your time. NBD is realy cool, and I would like to
make it cooler.

Have a nice day,

Francis Giraldeau