Improve efficiency of Hyper-V attaching iSCSI volumes

[Luis Fernández Álvarez]

The Hyper-V driver in Nova is not very efficient attaching Cinder volumes to the VMs.

It always tries to refresh the entire connection to the iSCSI target:

https://github.com/openstack/nova/blob/master/nova/virt/hyperv/volumeutilsv2.py#L87

This is a time consuming task that also blocks additional calls during this time.

The class should be refactored to work in a more efficient way. Calling the 'Update' method everytime a volume is attached should be replaced by a more intelligent mechanism. As reported in https://bugs.launchpad.net/nova/+bug/1372823 a call to 'self._conn_storage.query("SELECT * FROM MSFT_iSCSISessionToDisk")' could help.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/249291
Committed: https://git.openstack.org/cgit/openstack/os-win/commit/?id=b72790bacfd356021b2dd870ade6c9c216fd14a0
Submitter: Jenkins
Branch: master

commit b72790bacfd356021b2dd870ade6c9c216fd14a0
Author: Lucian Petrut <email address hidden>
Date: Fri Nov 20 16:20:40 2015 +0200

    iSCSI initiator refactoring using iscsidsc.dll

    This patch adds a new iscsi initiator utils class,
    leveraging iscsidsc.dll functions.

    The advantages are:
    * Same error output as iscsicli, without the proccess spawn
      overhead
    * Improved overall performance, having finer control over
      the iSCSI initiator and avoiding unnecessary operations
    * Fixed bugs related to LUN discovery
    * Static targets are used instead of having portal discovery
      sessions. This will let us use backends that require
      discovery credentials (which may be different than the
      credentials used when logging in targets)
    * improved MPIO support (the caller must request logging in the
      target for each of the available portals. Logging in multiple
      targets exporting the same LUN is also supported). Also, a
      specific initiator can be requested when creating sessions.

    Closes-Bug: #1403836
    Closes-Bug: #1372823
    Closes-Bug: #1372827

    Co-Authored-By: Alin Balutoiu <email address hidden>
    Change-Id: Ie037cf1712a28e85e5eca445eea3df883c6b6831

[Davanum Srinivas (DIMS) (dims-v)]

Anything else to do in Nova?

[Claudiu Belu (cbelu)]

Don't think so.

[Claudiu Belu (cbelu)]

No change was necessary to be done in nova. The issue has been addressed in os-win. Removing nova.