OpenZFS: adding support for Chacha20-Poly1305 encryption

OpenZFS: adding support for Chacha20-Poly1305 encryption In 2021, while at Fastmail, I oversaw rebuilding our mail storage architecture around OpenZFS. I rapidly became enamoured of it, and with over a year of serious experience now under my belt I’ve pretty much settled on it as the only option worth considering for serious storage. In mid-2022 I was playing with it on some small devices I had at home, and noticed that enabling encryption was adding substantial overhead, to the point of being almost unusable on low-powered devices like the Raspberry Pi. I think these days encryption should be table stakes for any filesystem, so I set out to find out why.