I found it curious that there is so much hardware that is at around 20% utilization. Wouldn't it be better to have less hardware with higher utilization and buy cheaper/better hardware later if warranted?
10 servers running at 20% utilization. Two servers experience hardware failure. What's the resulting utilization per server?
4 servers running at 50% utilization. Two servers experience hardware failure. What's the resulting utilization per server?
Which approach affords greater redundancy and room for growth?
Chance of hardware failure in a modern server in a colo, assuming it's been stress tested to find DOA hardware before being put in production? Low.
A quick spec on Dell's site, rough guess for the SSDs, the web servers are running around $4,000 each, or $4,500 with better warranty. Saving of 6 servers is >$20,000.
It's entirely up to their funding and growth plans and risk acceptance if that's a useful saving, but if they were a ramen-profitable-is-goal-one startup, it would be months of runway.
The original comment is based on the assumption that less hardware would still easily support the same traffic level.