>>>The Company ID, VSI, and VSIE are generated by LIO based upon the
>>> current vpd_unit_serial configfs attribute value.
>>>
>>> So as long as vpd_unit_serial is persistent, and the same value for
>>> backend devices across export failover to different nodes, Xen will
>>> always see the same EVPD information.
>>>
>>> Are you saying that vpd_unit_serial is already persistent across export
>>> failover, but Xen is still having problems..?
>>>
>>> Have you confirmed with sg_inq -i both before and after the export
>>> failover occurs..?
Hi Nicholas,
Sorry for how long it's taken me to reply but I wanted to let you (and the mailing list) know this is this resolved with great thanks to your explanation of how the vpd_unit_serial works in relation to the SCSI ID.
Once we enforced the vpd_unit_serial on each of the LUNs we can consistently fail over between iSCSI servers without the SCSI ID changing.
For reference for those using Pacemaker + Corosync with the LIO target:
primitive iscsi_lun_r1 iSCSILogicalUnit \
op monitor timeout=10s interval=30s on-fail=restart \
op start timeout=20s interval=0 on-fail=restart \
op stop timeout=20s interval=0 on-fail=restart \
params target_iqn="iqn.2003-01.org.linux-iscsi.s1-san5.x8664:sn.cb568058d955" scsi_sn=bff3f42a-49d8-4cfc-b64e-2b933e98141d lun=1 path="/dev/drbd1" allowed_initiators="iqn.2015-05.com.example:516c8f8c iqn.2015-06.com.example:2dcd27e0 iqn.2013-09.com.example:e611b8f2 iqn.2013-11.com.example:aef3bcea iqn.2015-06.com.example:3577646c iqn.2015-05.com.example:3367ed85 iqn.2015-07.com.example:0467ccce iqn.2015-11.com.example:40ee457b" implementation=lio-t
Note the scsi_sn parameter being passed in, this is what enforces the vpd_unit_serial as per https://github.com/ClusterLabs/resource-agents/blob/master/heartbeat/iSCSILogicalUnit#L367
Such a simple fix to something that for a long time we thought was unrelated.
I plan to write a quick blog post up on this as there are a lot of other people having this issue with Xen and it's clearly quite easy to fix when you understand the relationship as you pointed out.
Thanks again,
Sam McLeod.
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