Archive for April, 2011

Want to become an ESXi expert? here is how…

VMWare has released a three hour training video plus a free ebook to take you through the new features of ESXi 4.1, it’s worth looking at for VMware and system administrators.

I hope you find this training useful.

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Patch scan or remediation is not supported on “ServerName” because of unsupported or unknown OS

Coming from a WSUS era, VUM has provided flexibility and good patch/remediation management for virtual machines until you start seeing this error message “Patch scan or remediation is not supported on ServerName because of unsupported or unknown OS”, this has hit me hard especially moving forward to x64 versions of Windows 2008 R2 and Windows 7.

Vmware has released vSphere compatibility matrix found here. I have taken a snippet of this document shown below:


“Update Manager 4.1 and its subsequent update releases are the last releases of the product to support scanning and remediation of patches for Windows and Linux guest operating systems and applications running inside a virtual machine.” Supported document is found here. Make sure you rethink your patching management and deployment strategies for VM environment, I guess WSUS is still the way to go within Windows environment or purchasing MS System Centre Configuration Manager which makes software updates (not just windows updates) much easier with better control with other capabilities on top.

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Vmware Snapshots and VM Performance

I am sure you have read or come across VMware best practices regarding snapshots. We use vDR in some of our backups in addition to Backup Exec to backup specific applications such as SQL and Exchange.

As a note, VMware snapshots are crash consistent and not application consistent. For that reason VMware do not recommend using snapshots on DC servers. To have an application consistent backup, Backup Exec and other third party backup application can do that for you.

Now back to our issue, running on multiple snapshots is bad. It is even worse when having multiple snapshots on one machine older than 3 days. Your machine would struggle reading from these multiple delta vmdk disks to recreate your data. These snapshots can get very large and can degrade the performance of the server immensely! We had this issue with an Exchange server that had 7 snapshots over 3 days old at various sizes, the server became unusable. The time it took to delete those snapshots were close to 10 hours and that wasn’t fun!

To avoid this crisis, setup alarms on your VCentre to cascade to all nodes in your cluster to alerts you for any VM running on snapshots.

There is a great KB article by VMware.

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