Changes to the handling of local storage for the libvirt driver

Currently Libvirt and Xen virtualisation drivers for OpenStack Nova handle local storage differently. The amount of of local space reserved for an instance is determined by the instance type (i.e. flavor) and known as local_gb, here comes the difference.

The Libvirt backend:

  • Downloads the image from glance
  • Tries to resize this image to 10GB (can be adjusted using --minimum_root_size flag)
  • Attaches a second disk (known as disk.local)with the size of local_gb to the instance

The Xen driver:

  • Downloads the image from glance
  • Creates a vdi from this image
  • Resizes a vdi to the size of local_gb

We decided to add to the Libvirt backend optional ability to work the same way as Xen backend does:

To enable this strategy you need to add --disable_disk_local=true flag to your nova.conf. The drawback of this strategy is that you cannot use m1.tiny flavor anymore because it has the local_db set to zero. All other flavors work properly.

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3 thoughts on “Changes to the handling of local storage for the libvirt driver

    1. Boris Filippov

      It’s new feature, we don’t port it in upstream yet. In this moment you can use it either by installing OpenStack from our repositories (http://yum.griddynamics.net/yum/diablo for RHEL and http://yum.griddynamics.net/yum/diablo-centos for CentOS) or by acquiring nova sources with feature included from our github (https://github.com/griddynamics/nova). In case when you use RPMs, this guide should help you (fairly simple, for testing purposes): http://www.griddynamics.com/openstack/setup_single.html

      Reply
  1. 303bob

    Using VMware ESXi 4 having issues with libvirt. Diablo using libvirt 0.9.6-2 doesn’t seem to support VMware. Seems Essex will use libvirt 0.9.7. Anyone having success with OpenStack on RHEL using ESXi for libvirt?

    Reply

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