Yocto builds hog disk space. There are a few things you can do to reduce this:
yoe_clean_sstate
(cleans up your sstate)- remove the tmp/work directory (can be easily re-populated with sstate)
- share downloads and sstate-cache between builds
But, in the end, if you are supporting a full-featured project and doing regular releases from a Yocto snapshot, you’ll need ~256GB per project, especially if you are building things like QtWebEngine. Add in some test builds, work on new stuff, etc, and pretty soon you are bumping up against 1TB. Support multiple projects, and 2TB is soon gone.
If you are supporting several Yocto-based products, 2TB is probably the minimum you should consider today.