If an ISCSI NetApp storage array is refreshed within Oracle VM Manager after a LUN is unmapped at the array, and then refreshed again after the LUN is mapped back the second refresh may hang.

This is due to the fact that the Oracle VM Server sees the LUN size as zero and fails the multipath path to the LUN while the default path checker for NetApp TUR sees the path as up. The vacillating path statuses can cause IO to the affected LUN to hang.

Remapping LUNs is risky because it can data corruption since the targets have been switched outside of the server.

Workaround: One way to ensure that the Oracle VM Server maintains a consistent view of the path and avoids a possible hang scenario is to change the path checker for NetApp in mulipath.conf to directio. Note that directio is not considered as performant as TUR. Running the following command on the affected Oracle VM Server clears the hang:

# iscsiadm -m node -R

Bug 18421164