storage options for mySQL

I am working on a DB that consumes 700+GB, running on a 500GB Mac Pro. Some tables can be stored on a DAS without significantly compromising performance, but others are frequently modified/reindexed and there is a major performance drop if they are stored externally.

Can someone briefly summarize (external) storage options, considering cost and performance? (e.g. USB 3.0 RAID 0 SATA vs SSD)

I am aiming at 1TB external solution. I currently store 400GB externally and 200 internally. Works...

storage options for mySQL