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A Sizing Study of Lync® Server 2010 and its Back End SQL Database on Dell™ PowerEdge™ Servers
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 Total Number of Data Conferences Active
 Distribution List Calls per second
 CAA Calls in progress
Results and Analysis
Three test scenarios were run, and the results were collected from the Front-End VMs, Host, Monitoring
Server Reports and the Stress and Performance Tool counters. The three major scenarios in the testing
included:
Test Scenarios
Table 10.
Scenario
Number
of VMs
Total Number
of Users
Users
per VM
Hostnames of running VMs
Scenario A
1
3000
3000
FrontA
Scenario AB
2
6000
3000
FrontA, FrontB
Scenario ABCD
6
4
12000
3000
FrontA, FrontB, FrontC, FrontD
In Scenario A, one front end VM – named FrontA – was running with a total of 3000 heavy users. In
Scenario AB, FrontA from Test A was running with a 3000 users, and an additional VM named FrontB
was added that supported an additional 3000 users, resulting in a total of 6000 heavy users. In Scenario
ABCD, two more virtual machines were added, each supporting 3000 additional users for a total of
12,000 heavy users. This scenario involving 4 VMs was used in creating the reference configuration.
The Reference Configuration uses four Front End servers across two R720 Hyper-V hosts, and in the
worst case, support all four VMs on a single physical host (scenario ABCD). If one of the R720 Hyper-V
hosts goes offline, the two Front End servers running on it can be migrated to the other operation R720
Hyper-V host. In that instance, there would be a worst case of four Front End VMs running on a single
Hyper-V Host. The three test scenarios were conducted on a single R720 Hyper-V host, which due to its
identical system board, memory, and processor, will perform similarly to a R620. Scenario AB
represents normal operation in the Reference Configuration (Figure 14) and Scenario ABCD represents
the worst case scenario in the Reference Configuration. To study the scalability of the R720 platform
with increasing Lync Load, ―Scenario A‖ investigated the performance of a single VM.
To present our analysis of these results, first the Front End Server VMs performance is discussed,
followed by the results of the Hyper-V host’s performance. Third, the Lync QoE thresholds are verified
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These scenarios assume 3000 users per VM. Per Microsoft guidance, the recommendation is 2500 users
per VM (http://www.microsoft.com/en-us/download/details.aspx?id=22746). Our sizing tests indicate
that though an extra 500 users can be accommodated on each VM, the Microsoft recommendation is
representative of real-world Lync scenario with video, web conferencing and PSTN capability. Hence,
the Reference Configuration is sized for 2500 users per VM or 10,000 total users.