Number of machines


In the last problem where data size 30 TB and 72 GB Ram we calculated the number of machines as 420 i.e 30/72.
But in this solution, we have used the approach data/hard disk size.
Im confused


In the first problem, our primary concern was latency(which is what CACHE is used for) so we used RAM, but here we have lots of data and latency is not the primary concern. So we are using HDD.