vCenter Server 4.1 DRS Groups
One of the great new features of VMware vCenter 4.1 is Distributed Resource Scheduler (DRS) Groups. DRS Groups provides functionality that allows separation and placement of virtual machines onto specific ESX/ESXi hosts within a DRS cluster. Using DRS Groups, limiting the available hosts to a virtual machine or group of virtual machines is simple. Why might you want to use DRS Groups? I can think of many great scenarios where I could use DRS Groups; though, I will discuss one specific example regarding vCenter Server placement.
It is probably safe to assume most VMware administrators have implemented vCenter Server as a virtual machine within a DRS/HA cluster. A virtual vCenter Server running within a DRS/HA cluster provides many great high-availability and manageability benefits; however, there is a specific challenge that has not been solvable until vCenter Server 4.1. In the event vCenter Server become unavailable, an administrator would need to connect directly to an ESX/ESXi host using the vSphere Client where vCenter is located to manage the server there (i.e. open a console connection, restart the vCenter server, power the vCenter server up, etc.). But because vCenter Server is running inside a DRS cluster it is sometimes very time consuming locating the specific ESX/ESXi host where vCenter is running if you have many ESX/ESXi hosts within the DRS/HA cluster. For example, if there are 12 ESX/ESXi hosts running within a DRS cluster; the vCenter server could be running on any one of the 12—could you imagine using the vSphere Client and connecting to up to 12 hosts before locating the vCenter Server? Could you afford wasting 20 minutes during an emergency trying to locate vCenter Server?
Using DRS Groups vCenter Server can be limited to run on a limited number of ESX/ESXi hosts within a DRS cluster. For example, using DRS Groups an administrator can designate three of the 12 hosts where vCenter Server can run. In the event vCenter Server becomes unavailable it would be much easier to locate vCenter if you know it is primarily running on any of three hosts instead of 12 hosts.
The following VMware KB article provides a starting point for you to further investigate DRS Groups: http://kb.vmware.com/kb/1022842 .
