What size SSD?

[Mookzen]

It should be noted that some of the SSD models perform different within their series depending on the capacity. That is to say that the 64GB version performs a tad slower than the 128GB one in the case of the Crucial M4, for instance. This in addition to the already mentioned capacity constraint concerns leads one to suggest going beyond 64GB.

Also, considering the M4 drives (superb choice those), sure enough the 128GB model seems to be the sweet-spot.

 

[Yamahahahahaha]

The 64GB version of the M4 is a fair bit slower than the 128GB, which is also a fair bit slower than the 256GB.

The key and important parts of having an SSD cache improves your latency from ~8ms down to 0.1, plus vastly improved random 4K R/W performance.

The 'Heavy Workload' Storage bench is not reflective of real world usage, it's more aimed at Worst Case performance.

If you get a 120GB+ SSD, you can have caching AND some SSD storage.