Fully RAM based databases are being used in more and more places. For a lot of use cases throwing ALL of your data into memory will have a major performance benefit.
But when should you use RAM vs SSD?
RAM is about $100/GB. SSD is about $30/GB.
SSDs have a finite performance of about 100MB/s for reads. The only time you should throw money at all RAM based scenarios is when you ned to get more performance than a SATA disk can give you.
Of course, this is obviously going to depend on your application.
Another thought. 100MB is close to 800Mbit which is close to 1Gbit. Gigabit ethernet is pretty much the only solution for networking at the moment.
Even if you DID have a box that could saturate the gigabit link you’re not going to get any better performance by putting it all in RAM.
One could use dual ports, but that’s only going to allow you to use two SSDs.
You could use 10GbE but that’s going to cost you an arm and a leg!
We’re going to deploy with 3 SSDs per box. This gives us a cheaper footprint as we can run with a larger DB however I’ll never come anywhere near the full throughput of the drive if I’m on GbE.