Re: [Nbd] Support for NBD over UDP

[Alex Bligh <alex@...872...>]

> On 26 Mar 2017, at 11:48, Wouter Verhelst <w@...112...> wrote:
> 
> Hi Nivin,
> 
> On Wed, Mar 22, 2017 at 12:07:19PM -0700, Nivin Lawrence wrote:
>>      I was unable to find a lot of details on NBD over UDP, could you please
>> let me know if this is supported (for read/write).
> 
> It isn't; NBD relies on the TCP sequencing and checksumming far too much
> currently.
> 
>> The objective is to achieve
>> the same functionality of server restart by keeping the server stateless so
>> that if the server has to be restarted, you could still have the clients
>> continue, which does not look like is the case with TCP. Possibly NBD has more
>> reasons than just TCP to support server restart, if so, could you please list a
>> few. 
>> 
>>     If not UDP, is there an option to restart the NBD server without impacting
>> the clients?
> 
> nbd-client has a "-persist" option which is meant to support connection
> restart when necessary, but I'm not sure how well it works currently
> (you'd have to check).

Also NBD as a protocol currently fundamentally relies on a certain amount
of connection state, as negotiated during the negotiation phase.

I think the stateless/non-stateless question is not necessarily linked
with UDP/TCP (as demonstrated by the fact that NFSv4 runs over both
happily).

-- 
Alex Bligh