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 second component of the flavor name is the amount of RAM, and the third component, if present, is the size of the 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. Its root disk has no redundancy (raid0) and is typically 20GB in size. "C" flavor VMs also have an ephemeral disk, which is created and destroyed with the instance. It resides on the local hardware running the VM.

A virtual machine of "p" flavor is intended to run for an indeterminate length of time. The root disk is small, only 2.2GB, with the operating system typically taking about 770MB of that. 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.