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Hi All,

Is there a way to find in cinder how many instances are attached to a volume?

Thanks & Regards,
Sneha Rai

From: RAI, SNEHA
Sent: Monday, July 1, 2019 5:26 PM
To: openstack-dev at lists.openstack.org
Subject: HPE 3PAR Cinder driver-Multiattach: Fails to detach second instance from volume

Hi Team,

There is a bug on 3PAR Cinder driver https://bugs.launchpad.net/cinder/+bug/1834660.
I am able to attach multiple instances to 3PAR volume but only the first instance gets detached successfully.
For the second instance, volume goes into detaching status due to "Host does not exist" error.

What is happening here is, the first detach call invokes _delete_3par_host() which removes the compute host entry from 3PAR which ideally should be done only when the last instance is to be detached.
It would be great if someone could help me understand if this needs to be handled in driver code or nova would internally take care of it.

Code changes done to support multiattach-https://review.opendev.org/#/c/659443

Thanks & Regards,
Sneha Rai
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