# Scaling > See also: [Scale an application](https://documentation.ubuntu.com/juju/2.9/howto/manage-applications.md#scale-an-application) In the context of a cloud deployment in general, **scaling** means modifying the amount of resources thrown at an application, which can be done *vertically* (modifying the memory, CPU, or disk for a cloud resource) or *horizontally* (modifying the number of resources), where each can be *up* (more) or down (*less*). In the context of Juju, scaling means exactly the same, with the mention that - Vertical scaling is handled through [constraints](https://documentation.ubuntu.com/juju/2.9/reference/constraint.md#constraint) and horizontal scaling through [units](https://documentation.ubuntu.com/juju/2.9/reference/unit.md#unit). - Horizontal scaling up can be used to achieve [high availability (HA)](https://documentation.ubuntu.com/juju/2.9/reference/high-availability.md#high-availability) – though, depending on whether the charm delivering the application supports HA natively or not, you may also have to perform additional steps.