[stgt] SCSI ID uniqueness: VMware initiator

FUJITA Tomonori fujita.tomonori at lab.ntt.co.jp
Thu Oct 25 07:46:42 CEST 2012

Sorry for the delay.

On Mon, 15 Oct 2012 19:25:50 +0200
Yaron Sheffer <yaronf at porticor.com> wrote:

> We are using tgt with VMware vSphere as the initiator. We run tgt on
> Ubuntu Lucid, and everything works fine until there are several of our
> target machines with one initiator. Then the initiator starts ignoring
> some of the targets. It turns out that vSphere requires a value called
> "t10 ID" to be unique for each LUN, even across multiple hosts. This
> value appears to be identical to the "SCSI ID" parameter displayed by
> tgtadm.
> * Is this a legitimate requirement? I have always thought that only the

IIRC, yes.

> * target name needs to be globally unique.
> Trying to work around the issue, we attempted to set the SCSI ID
> parameter for the LUN using this command: tgtadm --mode logicalunit
> --op update --tid $tid --lun $lun --params scsi_id="my id"
> * This syntax is undocumented. Can you please add it to the man page? Or
> * can I provide such a patch?

Please send the patch. I'll merge it.

> * More important: although the parameter was set correctly according to
> * tgtadm, vSphere reported the same "IET___..." value as before. This
> * could be a problem in tgtadm or a problem on the initiator's side. Or
> * else a misunderstanding on our part...

tgt concats 'IET' string and the specified string for SCSI id.

> Finally we just randomized the target ID value, which causes tgtadm to
> generate a somewhat randomized SCSI ID, and makes VMware happy. We
> also patched tgt-admin to dump the tid value and accept it back in its
> "execute" mode. I will gladly share this patch, but I suspect that it
> is the wrong thing to do from an architectural POV. Any opinions?

scsi id is supposed to be parsistent after reboot. We can't use random
values every time.
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