I'm using VMware vSphere 5.5 on an ESXi 5.5 Host to host a small private web site. Host server is an HP ProLiant 380 DL with 50 GB Ram, 1 TB SSD storage, 2 Intel Xeon 5550 CPU. There are 10 running VMs for handle services like dhcp, dns, mail, mysql, apache, ... There are 3 running VMware VMS : 1 VM for vSphere and 2 VMs for vCenter Operations Manager

I'm optimizing my configuration, actually I work on DNS VM. Bellow is the VM configuration in vSphere :

  • CPU : 1 vCPU
  • Reservation : 1024 MHZ
  • Share : Height
  • Share HT : None
  • Memory : 256 Mb

There settings are chooses help by vCenter Operation Manager Planning report "Oversized Virtual Machines" where I can read the following informations :

  • Configured vCPU : 1
  • Recommended vCPU : 1
  • CPU Demand of Recommended : 3.6 %
  • Configured Memory : 256 MB
  • Recommended Memory : 192 MB

This VM is an Ubuntu 14.04 LTS x64. When I use the htop command, I see a load average near 0.00. The very load average look like real due too low usage of DNS service.

So, I don't understand why my little VM for handle DNS service show a 100% CPU Workload in vSphere and vCenter Operations Manager.

I need your help for understand my mistakes.

Thank you so much,


  • 1
    I can't answer your question, but I want to point out that the minimum CPU requirement for 14.04 in CLI mode is 300 MHz. Just something to consider to not needlessly reserve CPU cycles. If you have the GUI installed then consider not doing that for a DNS server. It's not unreasonable to provide a vital service such as DNS with reservations, just make sure you don't reserve more than necessary or you'll potentially be missing that resource elsewhere. Sep 16, 2014 at 21:12

1 Answer 1


vCenter Operations Manager needs to be tuned for your environment and business hours. There are tunables you can set that impact its recommendations for VM sizing. The default thresholds are way too aggressive.

But in general, I don't see anything wrong with the recommendations you've. I actually think 256MB of RAM is too small, depending on what you intend to use the Ubuntu VM for. You don't really need to change anything. vCOPs isn't telling you that your CPU is using 100% of its resources.

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