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CPU utilization increasing after VMotion in a DRS enabled cluster

Duncan Epping · Jan 24, 2008 ·

VMwarewolf already posted this fix on his blog but had to remove it… Now VMware added it to their knowledge base. Check out the original article because it may change in time. For the lazy people I included how to diagnose the problem and more…

Diagnose the problem:

  1. Use the VI Client to log in to VirtualCenter as an administrator.
  2. Disable DRS in the cluster and wait for 1 minute.
  3. In the VI Client, note the virtual machine’s CPU usage from performance tab.
  4. In the VI Client, note the virtual machine’s memory overhead in the summary tab.
  5. Enable DRS in the cluster.
  6. Use VMotion to move the problematic virtual machine to another host.
  7. Note the virtual machine CPU usage and memory overhead on the new host.
  8. Disable DRS in the cluster and wait for 1 minute.
  9. Note the virtual machine CPU usage and memory overhead on the new host.

If the CPU usage of the virtual machine increases in step 7 in comparison to step 3, and decreases back to the original state (similar to the behavior in step 3) in step 9 with an observable increase in the overhead memory, this indicates the issue discussed in this article.

You do not need to disable DRS to work around this issue.

The workaround:

  1. Use the VI Client to log in to VirtualCenter as an administrator.
  2. Right-click your cluster from the inventory.
  3. Click Edit Settings.
  4. Ensure that VMware DRS is shown as enabled. If it is not enabled check the box to enable VMware DRS.
  5. Click OK.
  6. Click an ESX Server from the Inventory.
  7. Click the Configuration tab.
  8. Click Advanced Settings.
  9. Click the Mem option.
  10. Locate the Mem.VMOverheadGrowthLimit parameter.
  11. Change the value of this parameter to 5. (Note: By default this setting is set to -1.)
  12. Click OK.

To verify the setting has taken effect:

Log in to your ESX Server service console as root from either an SSH Session or directly from the console of the server.

  1. Type less /var/log/vmkernel.

A successfully changed setting displays a message similar to the following and no further action is required:
vmkernel: 1:16:23:57.956 cpu3:1036)Config: 414: VMOverheadGrowthLimit” = 5, Old Value: -1, (Status: 0x0)

If changing the setting was unsuccessful a message similar to the following is displayed:
vmkernel: 1:08:05:22.537 cpu2:1036)Config: 414: “VMOverheadGrowthLimit” = 0, Old Value: -1, (Status: 0x0)

Note: If you see a message changing the limit to 5 and then changing it back to -1, the fix is not successfully applied.

To fix multiple ESX Server hosts:

If this parameter needs to be changed on several hosts (or if the workaround fails for the individual host) use the following procedure to implement the workaround instead of changing every server individually:

  1. Log on to the VirtualCenter Server Console as an administrator.
  2. Make a backup copy of the vpxd.cfg file (typically it is located in C:\Documents and Settings\All Users\Application Data\VMware\VMware VirtualCenter\vpxd.cfg).
  3. In the vpxd.cfg file, add the following configuration after the <vpxd> tag:
    <cluster>
    <VMOverheadGrowthLimit>5</VMOverheadGrowthLimit>
    </cluster>
    This configuration provides an initial growth margin in MB-to-virtual machine overhead memory. You can increase this amount to larger values if doing so further improves virtual machine performance.
  4. Restart the VMware VirtualCenter Server Service.Note: When you restart the VMware VirtualCenter Server Service, the new value for the overhead limit should be pushed down to all the clusters in VirtualCenter.

Howto: Sending html email from the service console

Duncan Epping · Jan 23, 2008 ·

*** This article is from 2008, this does not work for ESXi, look at vCheck from Alan Renouf instead ***

When writing the “Checking the diskspace on your VMFS volumes” blog I assumed that most of you knew how to send an email from the service console. I received a bunch of emails from people who were interested in how to setup the html email functionality. Well, here it is:

A while back VMGuru.com hosted a script which enabled you to send email from the service console. I just browsed their site and it’s nowhere to be found. So I hosted it on my site, mind: I changed the script so that you are able to send HTML emails. [Read more…] about Howto: Sending html email from the service console

VMworld Europe 2008 sessions!

Duncan Epping · Jan 21, 2008 ·

Check out the already extensive list of sessions for VMworld Europe 2008! There are a couple of sessions I will attend for sure: VMware Infrastructure 3 Networking – Advanced Configuration and Troubleshooting, Smart Application Deployment – Moving Beyond VirtualCenter Templates and ESX Server best practices for performance. See you in Cannes!

Stage Manager beta available

Duncan Epping · Jan 21, 2008 ·

I already blogged about it, but the new product VMware Stage Manager is now available as a beta download. Try it! Key features in this release:

  • Rapidly create new multi-server software configurations (services)
  • Monitor resource usage on a per-service, per-stage and per-instance basis
  • Easily perform operations on a complete service (e.g. cloning, deploying, archiving, etc.)
  • Marshall changes across the service lifecycle, interacting with external process management/workflow system to ensure compliance with service transition policies
  • Maintain an archive of past service configurations supporting compliance and recovery operations
  • Maintain an auditable history of software configuration changes
  • Manage storage behavior on a per-stage basis to maximize storage efficiency
  • Control access to services on a per-service, per-stage and per-instance basis
  • Inherit then deploy services to resource pools created within VMware VirtualCenter

Checking the diskspace on your VMFS volumes

Duncan Epping · Jan 21, 2008 ·

On a regular basis I noticed that people forget to monitor the free diskspace of their VMFS volumes. I created a script that can easily be scheduled with crontab and mailed with smtp_send. You can send it as an html based email if you setup MIME correctly. (For more info on how to set this up, check this blog) The script creates an html file with a table in which the necessary info is dumped, if a VMFS volume has less than 10% free space that specific line will be yellow and if it’s less than 5% than that line will be red… [Read more…] about Checking the diskspace on your VMFS volumes

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About the author

Duncan Epping is a Chief Technologist in the Office of CTO of the Cloud Platform BU at VMware. He is a VCDX (# 007), the author of the "vSAN Deep Dive", the “vSphere Clustering Technical Deep Dive” series, and the host of the "Unexplored Territory" podcast.

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