CPU Ready Revisted – Quick Reference Charts

I've written in the past about how high CPU Ready values can cause performance problems in VMware vSphere environments.  For those who don't know, CPU Ready is a measure of the amount of time that a guest VM is ready to run, but the VMware ESXi CPU Scheduler on the host is not able to immediately allocate cycles to the guest because it is busy doing work for other VM's.  CPU Ready values are exposed through ESXTOP and in the vSphere Client. I'm often called into customer environments to do performance troubleshooting, and CPU Ready is one of the first performance measurements I check my … [Read more...]

High CPU Ready, Poor Performance

**Update** January 2013: You've probably found your way here by doing a search for 'High CPU Ready in VMware' or something to that effect.  Welcome, I'm glad you're here.  Give this article a read as it still has relevant content, then check out this newer post on CPU Ready, with some handy quick reference charts and more detailed info on the condition: http://vmtoday.com/2013/01/cpu-ready-revisted-quick-reference-charts/.  Thanks for reading! --Josh I ran into an issue with a customer today where a VM was performing terribly.  From within the guest OS (a Windows 2003 application server … [Read more...]

Storage Basics – Part VI: Storage Workload Characterization

Most of what I covered in Storage Basics Parts 1 through 5 was at a very elementary level.  The math I used to do IOPS calculations, for example, is only true under very certain conditions.  RAID controllers implement caching and other techniques that skew the simple math that I provided.  I mentioned that the type of interface that you ought to use on your storage array should not be randomly chosen.  In fact, choosing the right array with the appropriate components and characteristics can only be done when you enlighten your decision with a characterization of workloads it will be … [Read more...]

The Skinny on ESXTOP

A reader named Mark contacted me today and asked if there was a way to reduce the size of the batch output from an ESXTOP run.  And he asks for good reason: Depending on the number of VM's on your host, the delay between ESXTOP samplings and the number of samples you collect, using the All Stats option (-a) can yield a massive file in a short period of time.  If written to a partition on your ESX Service Console you run the risk of filling the partition, and forget about actually being able to analyze the data in PERFMON or Excel.  For example, on an ESX host running ~15 VM's I produced 100MB … [Read more...]

ESXTOP Batch Mode Analysis with Windows Perfmon

I needed to grab some stats from my ESX hosts for off-line analysis so I fired up my trusty ESXTOP intent on using batch mode to capture a .csv formatted output.  I started to manually select the counters I was interested in while working in ESXTOP interactive mode (you can save your selected counters to the esxtop configuration file with the 'w' command) and thought that there must be a better way.  I found that better way in the VMware Performance Community: http://communities.vmware.com/docs/DOC-3930.  There is now a -a switch that can be used to include ALL performance counters.  I'm … [Read more...]