- SSD to SSD will be fastest.
- HDD to SSD will be usually be second - hdd reads are faster then writes but if you are compressing to more then about 5 times the reverse may be true (exact ratio depends on speeds of devices. I assume HDD is 100mbit, SSD is 500 mbit. YMMV
- SSD to/from HDD will be faster then HDD to HDD
The relative differences will depend on the speed of compression - if it's heavily CPU bound the differences will be less noticeable then speed optimised compression