Personally I keep the master copies of my music on a NAS (actually two NAS units) but the PlayIt Live "working" copy is on a SSD on the playout PC.
The "working" copy also has MP3 gain run over new files.
A little reading on backups:
Nathan De Lai
Hi Everyone, i have my Music Data Stored on a NAS (Single Studio ATM)
when i do plan out future upgrades is there any preformance bottleneck i should be weary of while running GBit Lan