Why not putting your lib on Thunderbolt ssd ?

If I had to put  my system and lib on the same ssd, I will make a volume for each ; but it is better to have separate ssd for each

look at this;

If this solution is slower than th internal drive you can put your system on it and put your lib in the internal ssd :

We just completed a review of the Seagate Thunderbolt adapter which is designed for Seagate's line of GoFlex portable hard drives. The Thunderbolt adapter is appealing, but with current Seagate externals it can only go so far, equaling USB 3.0 and FireWire 800 speeds due to the limitations of the external hard drives offered. What's really interesting though, is the Thunderbolt adapter uses a standard SATA interface for data and power, meaning users could buy the $99 sled and connect pretty much any 2.5" hard drive to SSD to take full advantage of the Thunderbolt port, without paying the massive premium for current pre-packaged external Thunderbolt storage options. That's exactly what we did, pairing the Thunderbolt adapter with the Intel SSD 520 and showing how much performance scales from USB 2.0 to native SATA.

You can alway try on the super fast internal, but make two volumes , one for system, one for VSL samples

It is not the system that will use bandwidth, it is reading VSL samples