Musings of a PC

Thoughts about Windows, TV and technology in general

SCVMM 2012: Server Fabric Lifecycle

… or all about high availability, update management and dynamic optimization.

The goal of the HA feature in VMM is to ensure that a VM can recover from failure, e.g. the failure of a host, and to ensure that a VM can easily be migrated. Over and above the capabilities of HA in previous versions of VMM, VMM 2010 adds the ability to create & delete clusters, manage clusters in untrusted domains, have a non-HA VM on a cluster and have VMM Server itself HA. VMM 2012 also adds the functionality manage Citrix XenServer (over the already existing functionality to manage VMware).

Update management is a new feature of VMM 2012 and aims to keep Windows fabric servers up to date. The reason why this has been added to VMM is to enable management of the complete fabric from a single pane of glass – and that includes all aspects of the server fabric lifecycle.

The feature requires a pre-existing, dedicated, root WSUS 3.0 SP2 64 bit server. If the WSUS server is remote, the WSUS console is required on the VMM server. It supports WSUS in SSL mode.

VMM gets a catalog of updates from the update server. It points the fabric servers to the correct update server, i.e. configures the WUA agent on each fabric server.

A baseline is then created. The baseline is a logical grouping of updates to assess compliance. VMM provides two sample baselines for Security and Critical updates. You can assign the baseline to hosts, host groups and host clusters, plus VMM server roles (library server, PXE server, Update server and VMM server). You cannot assign it to VMs (running or stored) or VHDs in the library.

A scan is then conducted to see if the server is compliant or not for the assigned baseline. VMM leverages WUA for applicability and compliance. Scan is on demand and automatable using PowerShell. VMM then makes the server compliant by installing missing updates. Update installation progress can be tracked in the VMM console and remediation is on demand and automatable using PowerShell.

There is an orchestrated workflow for remediating a Hyper-V cluster whereby each node in turn is put into maintenance mode, evacuating the node using Live Migration, install the missing updates based on baselines assigned, take the node out of maintenance mode, go to the next node and repeat. It supports Windows Server 2008 as well as R2 clusters and is automatable using PowerShell.

Dynamic Optimization is another new feature of VMM 2012. It keeps a cluster balanced for resource usage; Live Migration avoids VM downtime and the feature does not require Operations Manager. It supports Hyper-V, VMware and Citrix XenServer clusters.

DO has two modes – manual and automatic, with the default being manual. The feature optimises for CPU, memory, Disk I/O and Network I/O. It optimises when resource usage goes above the DO threshold. There is a configurable level of aggressiveness … more aggressive = more migrations = more balanced. The default is least aggressive.

There is also Power Optimisation, which extends DO and can only be enabled if DO is in automatic mode. It optimises for the same resources as in DO and optimises when resource usage goes below PO threshold. What PO does is powers off and on the physical hosts when it can move guests elsewhere. It evacuates a host before powering off and ensures that evacuation will not cause other nodes to go above the DO threshold, or that powering off will not violate cluster quorum requirements. It leverages out-of-band management for power off/on.

I need to follow up with Microsoft on the cluster quorum requirements because as I understand it, an even-node cluster requires a file share witness, whilst an odd-node cluster doesn’t … so if you turn off any node in a cluster, you are changing the quorum requirements!


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