You can also use multiple HDDs in parallel using a RAID config. This will increase the write/read speeds of the RAID volume as well as add redundancy. A RAID10 setup using 4 disks of equal size is a good comprimise. 

nullcount

bitcoin

Valuable Recommendations for Running Your Full Bitcoin Node with Umbrel

r3drun3

> Avoid Mechanical Hard Drives

I agree with this, however I'm also looking into how to make it cheaper to run a bitcoin node.  I saw this in a bitcoin wiki (not sure if this is a legit wiki or not): https://en.bitcoin.it/wiki/Splitting_the_data_directory There is a shell script there that looks like it will move the blk* and rev* files in the blocks directory to a harddrive.  I've though about setting up a system that has a small SSD to speed things up and then periodically run that script (with bitcoind stopped) to move that data to a big HDD.

At the end of the day it almost doesn't make financial sense to buy a HDD over a 2TB SSD.  You can even get by with a 1TB SSD for the blockchain data right now and those can be had for less than $50 USD now-a-days.