Re: Re: Re: [PATCH v2 06/11] transport-fabrics: introduce command set

[zhenwei pi <pizhenwei@bytedance.com>]

On 6/6/23 00:30, Stefan Hajnoczi wrote:
[snip]
> > > > +
> > > > +The Target ID of 0xffff is reserved, then:
> > >
> > > Please move this after the fields have been shown and the purpose of the
> > > Target ID field has been explained.
> > >
> > > > +\begin{itemize}
> > > > +\item The Target ID of 0xffff MUST be specified as the Target ID in a Connect
> > > > +Command for the control queue.
> > > > +\item The target SHOULD allocate any available Target ID to the initiator,
> > > > +and return the allocated Target ID in the Completion.
> > > > +\item The returned Target ID MUST be specified as the Target ID, and the Queue ID
> > > > +MUST be specified in a Connect Command for the virtqueue.
> > > > +\end{itemize}
> > >
> > > What is the purpose of the Target ID? Is it to allow a server to provide
> > > access to multiple targets over the same connection?
> >
> > A target listens on a port, and provides access to 0 or more targets. An
> > initiator connect the specific target by TVQN of connect command.
> > An initiator could connect a single target, multiple initiators could
> > connect the same target(typically, shared disk/fs).
>
> Why is the target ID separate from the TVQN? If the Target ID is a
> separate parameter then users will have to learn additional
> syntax/command-line options to specify the TVQN + Target ID and that
> syntax may vary between software.

The TVQN is the location of a target, for example:
virtio-tcp://192.168.1.110:8549/blk-dev/hdd-pool/238151a7-acd7-4621-bbdf-382ddbccb6a1

A target can be shared by multi initiators, they accesses the target by 
the same address(transport: tcp, ip: 192.168.1.110, port: 8549, TVQN: 
blk-dev/hdd-pool/238151a7-acd7-4621-bbdf-382ddbccb6a1):

Initiator_A launches Control Queue, issues connect command, gets the 
Target ID of Target_A(typically, dynamically allocated by target), then 
virtqueues connect to Target_A.

Initiator_B launches Control Queue, issues connect command, gets the 
Target ID of Target_B(typically, dynamically allocated by target), then 
virtqueues connect to Target_B.

...

Once an initiator disconnects, the target should reclaim the Target ID.

[snip]

--
zhenwei pi