I was at a client’s office helping them redesign their data center using VMware. We had already completed an assessment on their environment and had a good picture of what their server’s peak and average utilization time were. Now it was a matter of talking to each admin and making sure we understood what each server did, and what they required. A lot of their servers had specific hardware requirements that couldn’t be virtualized like specialized interfaces for the security systems, voicemail, PBX, etc…So we sat down with their system administrators one by one and talked about their servers. As I expected, there was one administrator who was digging his heals into the ground and didn’t want anything virtualized. His main reason was “high CPU utilization”. “That server really pounds the CPU.”

I have to admit, he was right. Some of his servers averaged <70% during peak hours. If he was using newer hardware I would have agreed with him. However, almost all of his machines had only 1 CPU with an average clock speed of about 1 GHz. So I did the math with him:

70% of 1 GHz is roughly 700 MHz of processing.

700 MHz is roughly 22% of a 3.2 GHz processor’s capability.

700 MHz is also roughly 5.5% of a 4 way server with 3.2 GHz CPUs. (..and about half that if they are dual core CPUs.)

The bottom line is that a process that utilizes a lot of a slower CPU, doesn’t use as much on a faster CPU. That’s the whole reason we’ve been buying faster machines, to get better performance. This is really important when determining what, and how to consolidate your servers.

When we were finished, he had a lot better understanding of Virtualization, and was more comfortable with migrating his systems to VMware.