they are identical.

 

note: other audio APIs call this a "buffer". some, like ASIO, force a double "buffered" model where the total size of the hardware memory area used for transfers (what ALSA calls the "hardware buffer") is always twice the "buffer size".

ALSA offers control over *both* the "period" (between interrupts) and the total hardware buffer size. This is unusual among audio APIs, except that JACK follows the same convention in its ALSA backend. You can specify the period size (-p) and the number of "periods" that make up the hardware buffer.