Specifications

13 Reference Architecture | Dell
TM
Unified Communication Solution with Microsoft® Lync® Server 2013 for Single Site
Implementation | Version 1.0
• Application-level high availability entails utilizing multiple instances of server roles to provide
services in the event of a failure. By ensuring that there is no single point of failure at the application
level, service downtime to the end user is minimized.
• Infrastructure high availability is provided when a hardware resource fails; there is another
preconfigured resource that takes over.
It should also be noted that during scheduled downtime, infrastructure availability ensures that there are
additional hardware resource, and the application-level availability will keep the application services up for
the end users. This is particularly important to IT administrators who wish to apply patches or upgrades to
their data center equipment.
3.1.2 Application Performance
While maintaining high availability is critical, applications must still perform well to ensure a reliable end-
user experience. The Dell Global Solutions Engineering group performed detailed verification to ensure that
the reference architecture presented is appropriately sized to meet the needs of a 1,000-user Lync
deployment. Some of the workloads sized in this reference architecture included audio conferencing, video
conferencing using multi-view, application sharing, distribution list expansion, address book downloads and
instant messaging. In order to size these workloads, the Microsoft Lync 2013 Stress and Performance Tool
was used.
It should also be noted that following application best practices help prevent performance bottlenecks.
These best practices are detailed in the next sections. Some of the major ones include:
• Static memory allocation, instead of dynamic memory allocation for virtual machines (VM)
• Virtual CPU to physical core ratio maintained at 1:1
• No co-existence of like roles on the same host
• Dedicated hard drive spindles for hypervisor, virtual machine (VM) and SQL data stores
3.1.3 Resource Consolidation
The final design consideration, in addition to availability and application performance, is resource
consolidation. In such a solution that touches Lync, voice gateways/session border controllers, and PSTN or
PBX systems, it is important to consolidate multiple components to the best extent possible and reduce data
center footprint and cost.
In the context of this reference architecture, server virtualization is primarily used to consolidate the
different Lync Server roles and not leveraged to provide application high availability. High availability is
provided natively by Lync as opposed to using virtualization clustering and HA.
Another important consideration is the overall network architecture. While this reference architecture
provides guidance on networking and details on the host server networking configuration, the detailed
sizing and configuration of the end to end networking components are outside the scope of this reference
architecture.