5. Advanced Features
As these enterprise-class virtualization products have grown, more
features have been added, enabling them to cluster physical host
machines, move virtual machines seamlessly between hosts while still
online, and manage virtual machines from a single point of view. Most
of these features are identical between the two products, but have
different names. This section covers those naming differences and
describes the different features because they are referenced later and
have a direct effect on support in Lync Server 2010.
• Failover Clustering / High-Availability—Refers
to the capability to join multiple physical hosts into a cluster where
shared storage from a storage area network (SAN) is provisioned. When
running on a clustered set of physical hosts, a virtual machine can be
made highly available. If a physical host fails or restarts at some
point, the highly available virtual machines running on that host can
be automatically restarted on a different host. The virtual machine is
also restarted during this process similarly to if the power was turned
off and then back on.
• Live Migration / vMotion—This
provides the capability to move virtual machines between different
hosts in a cluster without any disruption of service or perceived
downtime. For example, a virtual machine that is online and running can
be migrated to another host while users remain connected to the virtual
machine. This is accomplished by the host machines transferring the
memory state of the guest over the network and then simultaneously
bringing the machine online on the new host while the previous host
removes its copy. Both host machines must remain online during this
process, and the virtual machine remains online as well.
• Virtual Machine Manager / vCenter—These
two products are Microsoft and VMware’s respective centralized
management suites. When using a single hypervisor, management of the
host and guest virtual machines can be done individually, but as more
hosts and guests are added to an environment, managing each host
separately can become tedious. These management products offer a
centralized view and configuration store of all the hosts and guests
within the virtualization environment.
6. Lync Support Guidelines
Lync Server 2010 brings a welcome change for many organizations in
terms of the support policy offered for virtualization. In Microsoft
Office Communications Server 2007 R2, only a few workloads were
certified for virtualization. In a nutshell, any component that used a
type of media was not allowed to be virtualized. This didn’t mean those
features wouldn’t function in a virtual environment; it just meant
Microsoft would not officially support a deployment with virtualized
servers handling media because it had not tested or designed the
product for those scenarios. This meant that web conferencing, A/V
conferencing, and telephony features were not supported in a virtual
deployment in OCS.
With Lync Server 2010, nearly all scenarios can be virtualized with
only a few exceptions. The most welcome change is that the web
conferencing, A/V conferencing, and telephony integration features are
now supported. This means that Front-End Servers handling media and
Mediation Servers handling SIP trunks or media gateway integration can
now be deployed in a virtual machine. The roles and features supported
for Lync Server 2010 virtualization are listed here:
• Standard Edition Front-End Server—Supported for presence, IM, Enterprise Voice, A/V, and conferencing
• Enterprise Edition Front-End Server—Supported for presence, IM, Enterprise Voice, and A/V
• A/V Conferencing Server—Supported for A/V conferencing
• Enterprise Edition Back-End Server—Supported for SQL Server store and file share server
• Edge Server—Supported for remote access, federation, public IM connectivity, presence, IM, Enterprise Voice, and A/V
• Director—Supported for authentication and routing
• Monitoring Server—Supported for the monitoring service and collocated SQL Server store
• Archiving Server—Supported for the archiving service and collocated SQL server store
Note
If archiving or monitoring communications
from a virtualized Standard Edition Front-End server, the archiving and
monitoring roles must be deployed on a physical server to fall within
the support boundaries. Microsoft has not provided an explanation for
this anomaly, but it is explicitly called out.
The only roles that cannot be virtualized for use in Lync Server
2010 are the IP-PSTN gateways or the survivable branch appliances.
Considering most of these appliances would require a physical telephony
connection that would be impossible in a virtual environment, this
should not be an issue for most organizations.
This support shift should open the option for many organizations to
fully virtualize Lync deployments. However, there are still some
significant support boundaries as listed here:
• Hyper-V 2008 R2 or VMware vSphere 4 Only—The
only supported virtualization platforms at this time are Windows Server
2008 R2 Hyper-V or VMware vSphere 4.0 products. This should include the
Hyper-V 2008 R2 standalone free product and both the ESX and ESXi
products from VMware. This means that older versions such as Microsoft
Virtual Sever 2005, Microsoft Windows Server 2008 Hyper-V, and VMware
ESX 3.5 are not supported for use with Lync Server 2010.
• No Live Migration—Live
migration or vMotion of Lync virtual servers is not a supported
feature. Because media traffic heavily depends on low latency and CPU
processing, moving a Lync VM between hosts can lead to a poor
experience for users by either degrading or completely disconnecting a
media stream.
• Cannot mix physical and virtual machines within the same pool—There
are some additional guidelines when mixing physical and virtual servers
for Lync, but the most basic one is that a pool cannot contain a mix of
physical and virtual servers. All servers in a single Front-End, Edge,
Director, or Mediation pool must either be physical or virtual to be
supported.
• Virtual Front-End pool required—To
virtualize roles such as the Director, Edge Server, or A/V Conferencing
Server, the associated Enterprise or Standard Edition Front-End Server
must also be virtualized. This means that if an organization deploys
the Front-End Servers on physical machines, the Director or Edge Server
cannot be virtualized. This negates a common scenario where it might
make sense to use physical hardware for a front-end pool, yet
virtualize a less intensive role such as a Director. The opposite case
is perfectly valid. Organizations can virtualize the front-end pool,
but use physical hardware for a Director or Edge Server.
