[stgt] SCSI ID uniqueness: VMware initiator

Yaron Sheffer yaronf at porticor.com
Mon Oct 15 19:25:50 CEST 2012


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 

* Is this a legitimate requirement? I have always thought that only the 
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?

* 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...

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?




*Yaron Sheffer*|Co-Founder and CTO, *Porticor Cloud Security*| T:+972 73 
7294673 <tel:+972-73-7294673> | M:+972 52 8698984 <tel:+972-52-8698984> 
| yaronf at porticor.com <mailto:yaronf at porticor.com> |www.porticor.com 

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