In this post, I’ll walk you through how I solved a growing CPU bottleneck issue in my homelab by upgrading the CPUs in my Dell Precision 7920. I’ll share the process, challenges, and cost-effective solution that allowed me to double my system’s CPU capacity.
The primary system in my homelab is a Dell Precision 7920 tower. I purchased it on eBay with 2x Xeon 5222 CPUs and 512GB of RAM about 2 years ago, replacing a pair of older HP DL360 Gen8 rack mount systems. The older HP systems had a pair of E5-2450L CPUs, 8 cores/ea at 1.8ghz for a total of 28.8ghz per system… but these systems were primarily constrained by RAM and not CPU. Based on some rough math, I made the decision to go from a total of 32 cores at 1.8ghz to just 8 cores at 3.8ghz.
In the first ~6 months, everything was great. Neither CPU or RAM were bottlenecks, everything was running well. However, as I added more and more nested environments (including nested VCF) I started running into CPU contention. Last year (early 2024), I knew that this cluster CPU usage was high. I could see from Aria Operations that CPU demand was well above the usable capacity most of the time.

Around that time I looked into replacement CPUs for this system. I attempted to drop in some very low cost Xeon Gold 6138 CPUs (1st Gen Scalable) as they were very inexpensive (around $50/pair). Unfortunately, these CPUs were not compatible with the RAM in this system. The memory configuration is 8x64GB 2933 MHz DIMMs, which really limited my CPU choices to only those which run at 2933MHz (based on the table on page 91 of the owners manual). The 2nd Gen Scalable CPUs were preferred, as they are not expected to be deprecated in the next major vSphere release (per https://knowledge.broadcom.com/external/article/318697/cpu-support-deprecation-and-discontinuat.html). I had decided the best two options would be the Xeon Gold 6238 (22cores/socket at 2.1ghz) or 6230 (20cores/socket at 2.1ghz). Around the time these CPUs were running about $500/ea (6238) or $350/ea (6230) from various eBay sellers. I decided to hold off on the replacement and instead turn off/on certain environments as needed instead of running them all the time.
A few weeks ago, when running most of my nested environments concurrently again, I was seeing high CPU use. I did a bit more research and confirmed that the 6238 and 6230 CPUs were still solid options for what I needed, but now the price had fallen to 350/ea (6238) or $95/ea (6230). The 6238 CPUs would provide a total of 92ghz of capacity, while the 6230s would deliver 84ghz. Given that the demand for the cluster is only around 45ghz, the lower cost 6230s were about 2x the capacity I needed like a solid option. I decided to pick up a pair of and get them switched out. In the chart below, you can see that a few days prior to the “Now” line, the usable capacity of this cluster more than doubled. Aria Operations now shows that we are >1 year remaining until CPU runs out.

Conclusion
I knew that CPU usage was high, and that the most obvious solution was to add additional capacity. Even after narrowing down the options to just two, helped primarily by memory constraints, having specific capacity history helped make the most cost-effective decision. Instead of spending $700 on a pair of 6238 CPUs, I was able to solve the issue with just $200 for a pair of 6230 CPUs. After making the change, reviewing the same chart confirmed that the issue is in fact solved.
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