The compute instance flavor (US spelling is correct here) defines the amount of CPU and RAM allocated to your virtual servers. The price per hour for a compute instance varies according to its flavor. Existing flavors can be found here: https://catalystcloud.nz/services/iaas/compute/

Our flavors are named after the amount of CPU and RAM they provide you, so you don’t need to consult our documentation to find out their specifications. We currently provide a number of common combinations of CPU and RAM, and are prepared to introduce new flavors if required.

A virtual CPU (vCPU), also known as a virtual processor, is a time slice of a physical processing unit assigned to a compute instance or virtual machine. The mapping of virtual CPUs to physical cores is part of the performance and capacity management services performed by the Catalyst Cloud on your behalf. We aim to deliver the performance required by applications, and to increase cost efficiency to our customers by optimising hardware utilisation.

Since virtual CPUs do not map one-to-one to physical cores, some performance variation may occur over time. This variation tends to be small, and can be mitigated by scaling applications horizontally on multiple compute instances in an anti-affinity group. We monitor the performance of our physical servers and have the ability to move compute instances around, without downtime, to spread out load if required.

Best practices

It is best to scale applications horizontally (by adding more compute instances and balancing load amongst them) rather than vertically. It is possible to scale compute instances horizontally without downtime. Resizing compute instance vertically (up or down) will result in a brief downtime, because the operating system needs to reboot to pick up the new configuration.