Re: Re: [virtio-comment] [PATCH v4 4/7] transport-fabrics: introduce command set

[zhenwei pi <pizhenwei@bytedance.com>]

On 8/1/23 08:25, Raphael Norwitz wrote:
> > On Jul 30, 2023, at 10:34 PM, zhenwei pi <pizhenwei@bytedance.com> wrote:
> >
> >
> >
> > On 7/30/23 07:28, Raphael Norwitz wrote:
> > > As noted in my high level feedback I think the protocol should have redirection semantics.
> > [snip]
> > > > +\end{lstlisting}
> > > > +
> > > > +\paragraph{Connect Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Connect Command}
> > > > +
> > > This would be a good place to introduce some kind of target-side redirect mechanism to support redirecting to another IP.
> > > Probably just another op/status code and message from the target for redirection?
> >
> > Redirect mechanism is not used widely in my practice. Instead, multi path mechanism is used a lot. Would you please share your experience on this?
>
> Agreed - multipath is more common in iSCSI implementations. How would you make multipath work for Virtio-o-F since you only have one TCP or RDMA connection per VQ?
>
> What concern do you have with redirection-based iSCSI implementations? Itâs conceptually quite trivial. We have published documentation on our implementation here: https://www.nutanixbible.com/5b-book-of-ahv-how-it-works.html .
>
> I imagine Virtio-oF implementations could do something similar to avoid reliance on a fixed IP.
>
> > --
> > zhenwei pi

Hi,

I'm not against redirect mechanism(like iSCSI implementations), but this 
leads complexity(especially to a draft version).

The alternative implementations in my mind of the first step:
- configure Virtio-oF IPs to DNS server. The initiator resolves the IP 
on connecting/re-connecting. (this looks like iSCSI redirection - use 
DNS server instead of iSCSI redirection server, but no additional 
specification definition is needed)
- Or, configure IP list to a initiator, the initiator select 
one(RR/random...) on connecting/re-connecting.

--
zhenwei pi