Armory depends on Bitcoin Core having the full blockchain. On some platforms Armory can even "seed" Bitcoin Core with a newer version of bootstrap.dat than the one usually used by Bitcoin Core, helping significantly on Bitcoin Core's startup time. But since Armory also has its own database, you unfortunately end up with two copies of most of the data, and once Bitcoin Core is up to date Armory needs to build this second database, which also takes some time (but is faster than Bitcoin Core's startup). Running Armory requires significant disk space.