[stgt] [PATCH] iscsi: target redirect support

[FUJITA Tomonori]

On Wed, 16 Jun 2010 15:53:27 -0700
Chandra Seetharaman <sekharan at us.ibm.com> wrote:

> 
> On Wed, 2010-06-16 at 12:36 +0900, FUJITA Tomonori wrote:
> > On Tue, 15 Jun 2010 12:13:32 -0700
> > Chandra Seetharaman <sekharan at us.ibm.com> wrote:
> > 
> > > > > In effect, (1) I think we need to be able to mark the redirector tgtd as
> > > > > such (with an option in the command line or such),
> > > > 
> > > > I'm not sure why we need this since sounds like you can avoid the
> > > > issue with a proper targets.conf.
> > > 
> > > Looks like using the targets.conf file itself avoids the problem...
> > > but...
> > > 
> > > having a separate "designated" redirector would allow
> > >  - to have single node to which the initiators always connect
> > >  - to run the "redirector" in a node which doesn't actually have the 
> > >    backing store
> > 
> > You can do it now. You can configure a target to be redirected
> > somewhere without adding luns.
> 
> By virtue of the backing store not being there... I see..
> > 
> > >  - avoid unnecessary creation of the threads for the luns (with 1 lun in
> > >    both of my targets, i see 10 more threads og tgtd).
> > 
> > What version of tgt do you use?
> 
> 1.0.3, I guess... Will try the latest.
> 
> > 
> > As I wrote above, you can configure a target having only lun0 to be
> > redirected. We create only one pthread per target. We don't create any
> > threads for lun0.
> > 
> > 
> > >  - Have the redirector definition in targets.conf itself (which would
> > >    mostly be the case ?!)
> > 
> > That's a different issue. We can configure the redirect via tgtadm
> > now. All you need to do is modifying tgt-admin to support it. No need
> > to modify tgtd or tgtadm.
> 
> If/when we add redirector support to tgt-admin, how the two tgtds
> (redirector tgtd and serving tgtd) know to treat the redirector
> instructions differently ? i.e redirector tgtd should use the
> information and "serving" tgtd should not. Basically the tgtd should be
> knowing if it is a "redirecting" tgtd or "serving" tgtd.
> 
> Details:
> targets.conf file 
> ---------------------
> <target iqn.2010-03.com.cluster1:01>
>         <backing-store /gpfs/file1>
> 		vendor_id cluster1
> 		product_id target1
> 		scsi_id cluster1_target1_lun1
>                 lun 1
>         </backing-store>
> 	initiator-address 10.0.0.1
> 	redirect-address  10.0.1.51
>         redirect-port     860
>         redirect-reason   Temporary
> </target>
> --------------------
> 
> And if i were to use tgt-admin to control the tgtds with the same
> targets.conf file,

Needs to use different targets.conf for each tgtd?

targets.conf doesn't support two tgtd daemons on the single host.

btw, if you run two tgtd for the performance reason, try the latest
(if your kernel support signalfd).
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