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When creating a virtual machine, this machine needs to have some specifications. It is for example important to know how many CPU's and how much memory the VM should have access to. In openstack the specifications of a VM is configured by selecting a flavor when the VM is created. The flavor contains information about how many CPU's and how much RAM the VM should have, in addition to how large (and fast) the default disk should be. The flavor can also give access to special resources like GPU's. Our flavors are organized in various classes which are further described in this page.

Be aware that we in 2022 are in a transition-phase from an old naming-scheme to a new naming-scheme.

  • The old naming-scheme is documented here.
  • The old flavors will be removed during autumn 2022.
  • The recommended upgrade-path from old flavors to new flavors is listed here.

The flavor naming format

At its core the flavors in our openstack-platforms are named with the following format: "<prefix>.<basic-specs>". The prefix is used to define what kind of VM it is (is it a prioritized or a regular VM? Does it have support for special CPU functionality or not?), while the "basic-specs" describes how many virtual CPU's and how much memory the VM should have. This results in flavors like so:

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  • General purpose compute:
    • gx: based on Intel Xeon CPU's
  • Prioritized compute. Used for some applications where short response-times are crucial, and it is proven that the general purpose is not sufficient.
    • px: based on Intel Xeon CPU's
  • Scavenger compute. For compute-loads which is not time-sensitive, but it is nice with as much CPU as possible, the schavenger scavenger class allows us to allocate many CPU's that can be heavily utilized without affecting time-sensitive applications running on the same hardware.
    • sx: based on Intel Xeon CPU's
  • Dedicated compute. Some compute-loads need dedicated hardware for predictible performance. Flavors of this class get dedicated CPU's not shared with anyone. 
    • dx: based on Intel Xeon CPU's
    • de: based on AMD EPYC CPU's.

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  • gx3s.8c32r.e500g: A flavor with Intel Haswell cores (gx3), default storage at a local SSD (s), 8CPU+32GB RAM (8c32r), and an extra disk of 500GB backed by the default storage configuration (e500g).

NVMe

Flavors that have NVMe-disks are described with the extension "nvme<SIZE>".

  • For instance the flavor "x5.12c64r.nvme3t2" have 12 Cascade-Lake cores, 64GB RAM and a 3.2TB NVMe-disk attached.

Custom flavors

Some of our tenants have requirements not fitting the "general purpose" use-cases, and is investing in dedicated compute-nodes equipped with accellerators, local storage and similar. These tenants usually gets custom flavors (Identified by the keyword 'custom' in its name) providing access to these resources. The meaning behind each of the custom flavors is given to the personell needing access.

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