Plus we have hardware accelerated AES in most CPUs for like 15 years now?! I encrypt all my devices in case they get stolen or something and since then, I never noticed any noticeable CPU load due to that anymore. Should be the same for storage systems. And if there's spinning disks or SATA inside, you don't even need to worry. That'll slow it down enough and you won't notice the CPU is doing stuff as well.