Comment 8 for bug 1195913

Reviewed: https://review.openstack.org/35214
Committed: http://github.com/openstack/nova/commit/b6eb64497836608a804e69b208bb4312fed0c049
Submitter: Jenkins
Branch: master

commit b6eb64497836608a804e69b208bb4312fed0c049
Author: Chet Burgess <email address hidden>
Date: Fri Jun 28 21:21:36 2013 +0000

    Support setting block size for block devices

    cinder now supports backend with different block sizes. Sometimes
    we need to set a specific block size or operations against the
    backend will result in I/O errors. Additionally its a good idea
    to tune the block sizes to the correct size as it can improve I/O
    performance.

    The basic disk configuration for libvrit now supports setting the
    logical and physical block size of devices. The block size info
    is stored in connection_info of the block_device_mapping table
    for later use.

    By default it does not set the block sizes which defaults to
    512 bytes.

    DocImpact:
    This feature requires libvirt 0.10.2+ and the QEMU or KVM
    hypervisor. If a volume has a custom block size, cinder considers
    it required. As such the hypervisor and libvirt version are
    checked during the attach_volume call. If the hypervisor is not
    supported or the libvirt version is too old the attach is
    aborted and an exception is raised.

    Change-Id: I77adc96b340680218f82bbef8f9ec14711d26a7f
    Fixes Bug #1195913