One unfortunately common scenario is a situation where someone made a very poor processor choice sometime in the past for a database server that runs a mission critical workload. When I do health checks for SQLskills, I encounter both good processor choices and some pretty bad processor choices.
One recent example was a 22nm, quad-core Intel Xeon E5-2407 v2 processor (Ivy Bridge-EN) being used in a Dell PowerEdge R320 one-socket server. The Intel Xeon E5-2407 v2 was launched in Q1 of 2014, and it was a part of the Ivy Bridge-EN family. The EN suffix means lower base clock speeds, smaller L3 caches, and lower QPI speeds compared to the EP suffix processors, which is not a good thing for SQL Server usage. If you want to know how to decode Intel Xeon processor numbers, Intel explains it here.
This particular processor has a base clock speed of 2.4GHz, no Turbo Boost, no Hyper-Threading, a relatively small 10MB L3 cache, and a slow 6.4 GT/s QPI speed. This processor was an extremely bad choice for SQL Server usage, and it would have been a prime candidate for my laptop comparison method that I discussed here. It did have the virtue of only costing $250.00 for the processor though!
Since this processor has four physical cores, it would cost $1,858.00/per core for SQL Server 2016 Standard Edition (for a total of $7,432.00) and it would cost $7,128.00/core for SQL Server 2016 Enterprise Edition (for a total of $28,512.00). This means you could be paying anywhere from 30X to 114X your processor cost for the SQL Server 2016 licenses, depending on which edition of SQL Server 2016 you purchased.
A couple of things in defense of the person who made this choice. First, the single-socket Dell PowerEdge R320 only supported Intel Xeon E5-2400 v2 family processors, and the 2.4GHz Intel Xeon E5-2407 v2 was at least a better choice than the even slower 1.8GHz Intel Xeon E5-2403 v2 they could have picked! The primary motivation here was probably to pick a low cost server, with a low core count processor to minimize their hardware and SQL Server licensing costs.
Given that sort of goal, a much better choice at the time would have been a two-socket Dell PowerEdge R620 server with just one quad-core Intel Xeon E5-2637 v2 processor. The E5-2637 v2 has a base clock speed of 3.5GHz, a 3.8GHz Turbo Boost speed, Hyper-Threading, a larger 15MB L3 cache, and a faster 8.0 GT/s QPI speed. It did cost a little more for the processor, at a price of $996.00. A base two-socket PowerEdge R620 would also cost a little more than a base one-socket PowerEdge R320, but the overall difference in hardware cost would be pretty negligible compared to the SQL Server licensing costs.
Using an analysis based on TPC-E scores, I estimate one Intel Xeon E5-2407 v2 would have a system CPU capacity of 192.16 with a score/core of 48.04. A single Xeon E5-2637 v2 would have a system capacity of 559.77, with a score per core of 139.94. That is quite a difference!
My new Pluralsight course, SQL Server: Upgrading and Migrating to SQL Server 2016 has just been published. This is my eleventh course for Pluralsight, but the complete list of my courses is here.
Building on this online course is a new three day class, IEUpgrade: Immersion Event on Upgrading SQL Server, taught by myself and Tim Radney. The first round of this course will be taught in Chicago from October 11-13, 2017.
Here is a link to the complete series about upgrading SQL Server.