[Stgt-devel] Multiple tgtd exporting same device.

FUJITA Tomonori fujita.tomonori
Sun Jun 29 23:05:00 CEST 2008

Please don't use utf character code.

From: Simone Gotti <simone.gotti at gmail.com>
Subject: Re: [Stgt-devel] Multiple tgtd exporting same device.
Date: Sun, 29 Jun 2008 17:56:39 +0200

> > > I'm already doing something similar with gnbd and now I'd like to do the
> > > same with stgt via iscsi.
> > 
> > You runs multiple tgt daemons on one machine and they export the same
> > file to initiators?
> > 
> > If so, you can't do that easily because SCSI protocol is not about
> > only READ and WRITE commands. For example, how can tgt daemons handle
> > RESERVE command?
> In fact I didn't thought about the RESERVE command (for the moment I
> won't need SCSI reservation). Gnbd uses it's own fencing to avoid the
> access to the exported devices instead of scsi reservation but requires
> the gnbd clients to be part of the same cluster of the gnbd servers).

It's not only about RESERVE command. SCSI protocol has lots of states
of a device.

> Probably a solution would be that the N tgtd should communicate each
> other the reservation state.

Again, it's not about reservation. Definitely, you should have such
for lots of things. It's pretty complicated.

> BTW. does/will tgtd support SCSI3 persistent reservation?

It would be but there are lots of things to do before that.

> Is/will the state be saved on local file system? Or how is it
> implemented?

tgtd keeps all the states internally.

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