Memory is good almost universally. You will want to watch your buffer sizes, though, as large buffers can also contribute to latency problems. If you aren't monitoring from the DAW or need immediate feedback (playing a MIDI keyboard, for example) then buffer up. If you are doing those things, then you'll want to experiment with buffer size until you find the one that works for you.
With disks, what matters isn't so much size as write speed. For recording multiple tracks, it becomes even more important. Get disks that spin fast, are on fast interfaces (firewire, USB3, etc...) and are also configurable in Raid 0 configurations for the fastest possible write speeds.
The caveat with Raid 0 is that you will want to record to it, but you wont want to use it for storage. If any of the disks in the array fail, you lose the data on the entire array. Just something to keep in mind.
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