Unified Communications Virtualization Sizing Guidelines

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This article provides specifics and examples to aid in sizing Unified Communications applications for the UCS B-series and C-series servers.

Application Co-residency Support Policy

All UCS tested reference configurations are sized for co-residency except for C210 M1 Tested Reference Configuration #1 (which is only sized to host a single VM of 7500 user capacity). Note that the tested reference configuration for UCS C200 M2 is sized for co-residency at a lower capacity per VM than UCS B200 or C210 so only supports a subset of Virtual Machine templates.

The max number of virtual machines supported per physical server depends on the hardware selected and the quantity and resource usage of selected virtual machine OVAs.

This policy applies to both Tested Reference Configurations and Specifications-based VMware Support. Note that Specifications-based VMware support allows hardware options that may support more or less VMs per physical server than a TRC.

To determine which applications may share a physical server, use the following guidelines:

  • Application mix on same physical server / vSphere ESXi host limited to "UC with UC only".
  • All applications must use a supported virtual machine OVA template (see Unified Communications Virtualization Downloads (including OVA/OVF Templates) for more information). All applications require a 1:1 mapping between virtual hardware and physical hardware. These rules apply equally to UC on UCS TRC, UC on UCS specs-based and HP/IBM specs-based.
    • All applications require a 1:1 mapping of VM vCPU cores to physical CPU cores. Cisco Unity VMs also require VMware CPU Affinity.
    • If there is at least one live Unity Connection VM on the server, then one CPU core per physical server must be left unused (it is actually being used by ESXi scheduler).
    • The sum of virtual machines' vCPU cores may not exceed the total physical CPU cores on the physical server (less one if hosting at least one live Unity Connection VM).
    • The sum of virtual machines' vRAM (plus 2GB for VMware overhead) may not exceed the total physical memory on the physical server.
    • For supported DAS deployments, the sum of virtual machines' vDisk may not exceed the physical disk space of the physical servers' logical volume(s) (based on RAID configuration).
  • For UCS B200 and C210 TRCs, you may otherwise mix and match applications/versions and VM OVAs (of any size) in any quantity as long as you do not oversubscribe any physical server resources as described above. Note that specs-based may allow a higher or lower VM count per physical server relative to UC on UCS TRC.
  • For UCS C200 M2 TRC #1, there are additional TRC-specific restrictions due to use of less powerful E5506 (2.13 GHz) processor relative to other TRCs (which use more powerful processors such as E5540/2.53 GHz or E5640/2.66 GHz). A C200 M2 configured with a different CPU allowed by specs-based does not have these TRC-specific restrictions. Follow these rules:
    • The only supported virtual machine OVA templates are:
      • CUCM - Unified Communications Manager 1000 users
      • CER - Emergency Responder 12,000 users
      • CUC or UCxn - Unity Connection 500 users, 1000 users and 5000 users
      • CUP - Unified Presence 1000 users
      • CUCCX - Unified Contact Center Express 100 agents
      • CUxAC - Unified Department, Business and Enterprise Attendant Consoles
      • Other unlisted OVA templates are not supported on C200 M2 TRC #1.
    • Otherwise at this time the following co-residency scenarios are supported:
      • Four VMs for Unified Communications Manager Business Edition 6000: CUCM 1000 users + CUC 1000 users + CUP 1000 users + CUCCX 100 users
      • Any other combination of CUCM, CER, CUC/UCxn, CUCCX, CUxAC, provided you keep a 1:1 vCPU to physical core ratio, have at least 1 unused physical core if there is one or more instance of CUC/UCxn present, and only use supported OVA templates for UCS C200 M2 TRC#1:

See the Sizing Examples at the bottom of this page for examples of using these guidelines.

Redundancy and Failover Considerations

Application-layer considerations (such as Unified CM Cluster over WAN or Unified CCE Remote Redundancy) are the same for virtualized (UC on UCS) or non-virtualized (MCS 7800) deployments.

However, since there is no longer a 1:1 relationship between hardware and application instances, "placement logic" must be taken into account to minimize the impact of hardware unavailability or unreachability:

  • Avoid placing a primary VM and a backup VM on the same server, chassis or site
  • For failover groups, avoid placing all actives on the same server, chassis or site
  • Avoid placing all VMs of the same role on the same server, chassis or site

Network, QoS and Shared Storage Design Considerations

See QoS Design Considerations for Virtual UC with UCS and Shared Storage Considerations.

Sizing Examples

This section shows a sample system configuration based on following the High-level Checklist for Design and Implementation for the following set of customer requirements:

  • General Requirements
    • Three sites - Headquarters (HQ) and two Branches (A and B)
    • CUCM and Applications located at each site
    • Up to 30,000 lines per sites
    • 100+ sites
    • Transparent use of PSTN if IP WAN unavailable
  • Headquarters (HQ) Requirements
    • 12K Phones, use Cisco TFTP server
    • 10K Messaging users
    • 10K users equipped with Cisco Unified Personal Communicator (CUPC)
    • Contact Center with 240 agents and 10 supervisors
  • Branch A Requirements
    • 2K Phones, use Cisco TFTP server
    • 2K Messaging users
    • 2K users equipped with Cisco Unified Personal Communicator (CUPC)
    • Contact Center with 145 agents and 5 supervisors
  • Branch B Requirements
    • 500 Phones, use Cisco TFTP server
    • 500 Messaging users
    • 500 users equipped with Cisco Unified Personal Communicator (CUPC)
    • Contact Center with 45 agents and 5 supervisors

After going through the design process, the following servers were selected to host the virtualized UC applications:

  • Six Cisco UCS B200 Blade Servers for HQ (running in a UCS 5100 Chassis connected to UCS 6100 Fabric Interconnect Switches), using TRC#1 (UCS-B200M2-VCS1).
  • Three Cisco UCS C210 General-Purpose Rack-Mount Servers for Branch A, using TRC#1 (UCS-C210M2-VCD2)
  • Two Cisco UCS C200 General-Purpose Rack-Mount Servers for Branch B, using TRC#1 UCS-C200M2-VCD2)
  • Note this example does not include non-UC applications (such as Cisco Nexus 1000V or Cisco Network Registrar) or 3rd-party applications such as customer-provided DNS / DHCP / TFTP servers, directories, email, groupware or other business applications. These applications need to run on separate physical servers and are not allowed to be co-resident with UC at this time. See the Co-residency section on this page for more details.


See below for details on the server layout and application/VM placement at each site. Note that Branch B is using UCS C200 M2 TRC #1 so has restrictions on which VM OVAs were able to be used.

HQ server detail:


Branch A server detail:


Branch B server detail:


Sizing and Ordering Tools

The suite of tools listed below can assist you with the sizing, configuring and quoting of Cisco Unified Communications solutions on the Unified Computing System.

Cisco Solution Expert

Cisco Solution Expert assists Cisco field and Cisco Unified Communications specialized channel partners in designing and quoting UC on UCS solutions using the Cisco Unified Workspace Licensing or the traditional design model. Solution Expert delivers a Bill of Materials for the Unified Communications software and the UCS B-series Blade Servers and VMWare ordered as Collaboration SKUS.

Netformx DesignXpert

Netformx DesignXpert is a third party application used to design and quote the Cisco Unified Computing System B-series. DesignXpert has two advisor modules that can be used to quote a Unified Communications solution with the Unified Computing System:

  • UC Advisor – a designing and quoting solution used to quote Unified Communications software. The UCS B-series Blade Servers and VMWare ordered as Collaboration SKUs can be quoted when ordering separate from the Unified Computing System. Other UCS B-series components must be configured via UCS Advisor below.
  • UCS Advisor - a design and quoting solution for all UCS B-series components including Blade Servers ordered as Collaboration or Data Center SKUs, UCS 5100 Blade Server Chassis, UCS 2100 Fabric Extender and UCS 6100 Fabric Interconnect Switch.

Cisco Unified Communications Sizing Tool

Cisco Unified Communications Sizing Tool delivers hardware sizing for complex Enterprise Unified Communications solutions, including Cisco Unified Contact Center Enterprise. The Sizing Tool delivers the virtual machine requirements for Unified Communications applications on the Unified Computing System platform.

Cisco Configuration Tool

Cisco Configuration Tool (need link here) is part of the suite of Internet Commerce Tools for managing online ordering of Cisco products. It enables you to configure products and view lead times and prices for each selection. The Cisco Configuration Tool, also known as the Dynamic Configuration Tool, is used to configure the Unified Communications products and the B series SKU and VMWare ordered as Collaboration SKUs.

Ordering Guides

Ordering Guides for Unified Communications System 8.x releases are available for Cisco sales, partners, and customers.

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