Hi Ayal,

Thanks for that - I was thinking the same after I did some more testing last week - e.g. shared a image file from a different iscsi target and the same iscsi target, the lun on the "same target" changed, the one on the "other target" did again the same - so I figured it had something to do with tgtd.

Thanks for below, I was looking into those options to try next week :) ...

Thanks
Alex


On 03/03/2013 06:34 PM, Ayal Baron wrote:

----- Original Message -----




Hi there,

I was doing some testing around ovirt and iscsi and found an issue
where as when you use "dd" to create "backing-stores" for iscsi and
you point ovirt to it to discover&  login, it thinks the LUN ID is
the same although the target is different and adds additional paths
to the config (automagically?) bringing down the iSCSI storage
domain.
There is no question about the behaviour, it's not a bug, that is the way 
multipathing works (has nothing to do with oVirt).  The GUID of a LUN has to be 
unique.  multipathd seeing the same LUN ID across multiple targets assumes that 
it's the same LUN with multiple paths and that's how you get redundancy and 
load balancing.
Why tgtd doesn't take care of this built in I could never grok, but what you 
need to do is edit your targets.conf and add the scsi_id and scsi_sn fields.

Example:
<target MasterBackup>
      allow-in-use yes
<backing-store /dev/vg0/MasterBackup>
          lun 1
          scsi_id MasterBackup
          scsi_sn 444444444401
</backing-store>
</target>

See attached screenshot of what I got when trying to a "new iscsi san
storage domain" to ovirt. The Storage Domain is now down and I
cannot get rid of the config (???) how do I force it to logout of
the targets ??


Also, anyone know how to deal with the duplicate LUN ID issue ?


Thanks
Alex





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