Virtual machine flavors

Parent page: CC-Cloud

Virtual hardware templates are called "flavors" in OpenStack, defining sizes for RAM, disk, number of cores, and so on. ... Flavors define a number of parameters, resulting in the user having a choice of what type of virtual machine to run—just like they would have if they were purchasing a physical server. - NetApp OpenStack Deployment and Operations Guide

By convention on Compute Canada clouds we prefix flavor names with a "c" to designate "compute" and a "p" to designate "persistent". The first component of the flavor name is the number of virtual cpus, the second is the amount of RAM, and the third, if present, is the size of secondary ephemeral disk.

A virtual machine of "c" flavor is intended for jobs of finite lifetime and for development and testing tasks. It starts from a qcow2-format image. It's disks reside on the local hardware running the VM and have no redundancy (raid0). The root disk is typically 20GB in size. "c" flavor VMs also have an secondary ephemeral data disk. These storage devices are created and destroyed with the instance.

A virtual machine of "p" flavor is intended to run for an indeterminate length of time. There is no predefined root disk. The intended use of "p" flavors is that they should be booted from a volume, in which case the instance will be backed by the Ceph storage system and have greater redundancy and resistance to failure. We recommend using a volume size of at least 20GB for the persistent VM root disk.