We're debating between:

  1. R820 - E5-4620 v2 - 2.6GHz - 8 cores, 20MB Cache, 1333MHz max memory speed - max of 768GB ram - 8 core
  2. R730 - E5-2620 v3 - 2.4GHz - 6 cores, 15MB Cache, 1866MHz max memory speed - max of 768GB ram - 6 core

I understand that we'd see better performance in the R820 for parallel processes, but would the R730's actually be better for SQL Server? Using a benchmark site it appears that the E5-2620 is faster (86.72 vs 70.30) but rarely is CPU the bottleneck on a SQL Server.

How should we decide? I am not asking for a product recommendation but what way to choose (SQL Server 2014 / rack mounted).

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    There are a lot of factors (not all hardware related) around this question.This article from SQL Performance outlines what is worth looking at in a CPU and addresses some specific models as well. – LowlyDBA Mar 23 '15 at 20:38
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    I'd probably go for the R730 as it's a newer generation machine. In theory this means it's faster, more efficient and you'll be able to get support for it longer. In theory. – Colin 't Hart Mar 23 '15 at 21:02
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    R820 comes with a 4 socket server which means there will be scaling issue like cross NUMA access which will have a hit of scalablity. Also, sql server licensing cost will be more in the R820 compared to R730. I would prefer the R730. – Kin Shah Mar 23 '15 at 21:19
  • Glenn Berry's post Dell 12th Generation Rack Mounted Server Comparison will help you as well. – Kin Shah Mar 23 '15 at 21:29
  • I am asking HOW to choose, please see the last line. I created a Meta question regarding this question to get it edited and reopened. – Dan Andrews Mar 26 '15 at 18:14

The way to gauge hardware performance is to be take a look at your current workload. So I would begin by quantifying that:

  1. Take a look at Brent Ozar's perf tuning stuff
  2. Identify your bottlenecks (are you seeing bad parallelization, CPU chugging away without finishing, memory, storage)
  3. Determine what differences there will be between your new and old system.

You're right that SQL Server rarely bottlenecks at the CPU, but it's not impossible and you can tell whether you're seeing a CPU bottleneck by looking at some perf counters.

Then you'll know whether or not you'll see a performance improvement simply by updating the CPU to a faster one or one with more cores. If your SQL isn't written to take advantage of parallel processing, it won't matter if you throw more cores at it.

Additionally, there's more things I would want to consider in buying a system:

  1. Upgradability - SQL Server will rapidly test the limits of your hardware if you let it, so try to anticipate that
  2. Affordability - SQL Server licensing in 2014 is core-based, so this should be a consideration.

This is in addition to other IT concerns you'd want to keep in mind like maintainability, support contracts, and your space/power requirements.

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