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I am trying to set up openstack on a single machine using devstack scripts. In configuration for cinder this parameter is given VOLUME_BACKING_FILE_SIZE. I am not able to understand what is the use of this parameter as we are giving name of volume group and any cinder volumes can be created in that volume group.

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1 Answers1

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In default configuration Cinder use iSCSI+LVM as storage backend.

LVM allows to create Logical Volumes belonging to a Volume Group, these Logical Volumes are actually created and correspond to the Volumes you create in Cinder.

Devstack automatically creates a Volume Group with a loopback device as Physical Volume. A loopback device is a fake device that actually refers to a file. VOLUME_BACKING_FILE_SIZE sets the size of this file.

So if you set this size to 10GB, you will be able to create Volumes for a total size of 10GB (i.e. 10 Volumes 1GB each one or 1 volume of 10GB).

  • so if i manually create a `Volume Group` and give this to devstack then there is no need to give `VOLUME_BACKING_FILE_SIZE` and devstack will start using my volume group instead of creating a loopback device. – shivams May 07 '15 at 06:39