How much disk space does a Malairte full node need?

A full node stores the entire blockchain, so disk is the resource you plan around first. The chain grows over time, so the right approach is to provision generous headroom above the current size rather than the bare minimum, so you are not migrating storage within months. A solid-state drive is strongly preferred over a spinning hard disk because the initial sync touches the disk constantly and an SSD makes that far faster. Keep an eye on free space as the chain grows, and upgrade storage before the drive fills, since a full disk stops the node cold.