Can Link Cloning be performed in Openstack ?

asked 2018-03-05 06:52:48 -0600

Shahid gravatar image

I was wondering if we can perform link cloning in Openstack which can reduce the amount of disk space and memory used if multiple users have to use same instance with same configuration. which can be better the just snapshot taken in cinder.

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If you use ephemeral storage, and the file type for ephemeral disks is qcow2 (the default; see https://docs.openstack.org/nova/lates...), then instances using the same image on the same host will actually use a COW file backed by the same base image.

Bernd Bausch gravatar imageBernd Bausch ( 2018-03-06 00:28:56 -0600 )edit

The effect is that little disk space is used for the root filesystem of an instance.

I believe that this is what you mean by Link Cloning.

Bernd Bausch gravatar imageBernd Bausch ( 2018-03-06 00:29:45 -0600 )edit

Basically a linked clone is a copy of a virtual machine that shares virtual disks with the parent virtual machine in an ongoing manner. Because a linked clone is made from a snapshot of the parent, disk space is conserved and multiple virtual machines can use the same software installation.

Shahid gravatar imageShahid ( 2018-03-06 00:48:16 -0600 )edit

OpenStack doesn’t create a parent-child relationship, but several instances can be based on the same disk. Thus, the disk space effect is similar to link cloning. But OpenStack doesn’t implement instance cloning at all.

Bernd Bausch gravatar imageBernd Bausch ( 2018-03-06 03:37:52 -0600 )edit

How can that be done ? Suppose I am having a windows instance of which I want to launch multiple sessions for different users based through the same disk.

Shahid gravatar imageShahid ( 2018-03-06 06:46:38 -0600 )edit