Cliff Hobbs is a UK-based systems management consultant who specialises in the various systems management tools covered by his website FAQShop.com such as Microsoft System Center Configuration Manager (ConfigMgr) and Systems Management Server (SMS).Having worked with SMS since 1998 Cliff has gained extensive experience of designing, deploying, and supporting large enterprise-wide systems management solutions on behalf of companies such as EDS, 1E and Getronics.In recognition of his contribution to the Systems Management community Microsoft awarded Cliff the Most Valuable Professional (MVP) award for SMS in January 2004 which has been re-awarded in all subsequent years.Having grown up with the PC from the days of the IBM AT and PC-DOS 3.3, he has an extensive knowledge of several operating systems and applications gained through his present and past employment with companies such as EDS, Du Pont, Abbey National and Getronics, amongst others.The prime goal of FAQShop.com is to help people use Systems Management technology to make their lives easier - not for technology to control their lives which is reflected in this site's mission statement:
'Ensuring you get the best of IT'.
From the SCVMM Team Blog:
One of the top questions that I keep hearing from our customers is to explain the ‘over-committed’ status and why we sometimes display this status. An example of when this status might be displayed is when attempting to migrate a VM to a particular host, depending on what is already on the destination the ‘over-committed’ status might be displayed.
HAVM Placement and “Over-committed” Status
When placing a highly available virtual machine, the placement process in VMM calculates whether adding a new virtual machine to a host cluster will over-commit the cluster based on the cluster reserve configured for the host cluster in VMM. The cluster reserve specifies the number of node failures a cluster must be able to sustain while still supporting all virtual machines that are currently deployed on the clustered hosts. If a host cluster cannot withstand the specified number of node failures and still keep all of the virtual machines running, the cluster is placed in an Over-committed state, and the hosts are not available for placement. An administrator can override this and place an HAVM on a host in an over-committed cluster during manual placement. Cluster reserves are a unique feature of VMM.
For example, if you specify a node failure reserve of 2 for an 8-node cluster, the rule is applied in the following ways:
· If all 8 nodes of the cluster are functioning, the host cluster is marked Overcommitted if any combination of 6 nodes (8-2) in the cluster lacks the capacity to accommodate existing virtual machines.
· If only 5 nodes in the cluster are functioning, the cluster is marked Overcommitted if any combination of 3 (5-2) nodes in the cluster lacks the capacity to accommodate existing virtual machines.
VMM’s cluster refresher updates the host cluster’s Over-committed status after each of the following events:
· A change in the cluster reserve value
· The failure or removal of nodes from the host cluster
· The addition of nodes to the host cluster
· The discovery of new virtual machines on nodes in the host cluster
The cluster reserve is set on the General tab of the host cluster properties. For a procedure, see How to View and Modify the Properties of a Host Cluster (http://go.microsoft.com/fwlink/?LinkID=162986).
The above information is available in the System Center Virtual Machine Manager 2008 R2 Operations Guide.
Download Virtual Machine Manager Documentation
http://technet.microsoft.com/en-us/library/ee441285.aspx
Mike Briggs | Senior Support Escalation Engineer
http://blogs.technet.com/scvmm/archive/2009/12/07/what-does-over-committed-status-really-mean.aspx