Problem

Multipath call failed exit. This warning occurs in the Compute log if
you do not have the optional multipath-tools package
installed on the compute node. This is an optional package and the
volume attachment does work without the multipath tools installed. If
the multipath-tools package is installed on the compute
node, it is used to perform the volume attachment. The IDs in your
message are unique to your system.

WARNING nova.storage.linuxscsi [req-cac861e3-8b29-4143-8f1b-705d0084e571
    admin admin|req-cac861e3-8b29-4143-8f1b-705d0084e571 admin admin]
    Multipath call failed exit (96)

Solution

Run the following command on the compute node to install the
multipath-tools packages.

# apt-get install multipath-tools