Today, we’re pleased have a guest post–The Might of UCS Mini for VDI – UCS+Nimble+Citrix–from Frank Anderson, Solutions Architect and Desktop Virtualization Performance specialist with Cisco’s Computing Systems Product Group.

You might have heard some of the buzz around one of Cisco’s newest offerings – the Cisco UCS Mini. It’s got all the power of Cisco Unified Computing System (Cisco UCS), but it’s small, compact, and versatile. You can use a Cisco UCS Mini as a workhorse in an enterprise data center, and at the same time, it’s optimized for remote offices, branch offices (ROBOs), and other small IT environments. Best of all, it’s an affordable option for any size enterprise.

And now, we’re bringing this compact solution into our virtual desktop infrastructure (VDI) solution landscape.

Add Nimble Storage and Citrix XenDesktop-based virtual desktops and you get a space-efficient, cost-effective ROBO compute and storage platform that is ideal for up to 500 users.

Yes, this Cisco UCS Mini desktop and application virtualization solution, with a Nimble Storage CS300 array running Citrix XenDesktop 7.6, provides all the power of Cisco UCS in a scalable, converged, and self-contained package. Here’s is a quick look at what this configuration looks like:


Remotely located, centrally controlled. 

Another great thing about this bundled solution is that it can easily be controlled and managed from an enterprise data center with Cisco UCS Central software. And with the Cisco Fabric Interconnect technology that’s built into the chassis, policy management, updates, and compliance are consistent whether the Cisco UCS Mini is in a centralized data center or used remotely. Plus, when there is a need for a solution in many locations, they can all be managed through a single plane of glass as if they were part of a corporate data center. This gives IT outstanding manageability over the entire Cisco UCS platform throughout the enterprise.

More power, better control.

In addition, companies can use Cisco UCS Director with Cisco UCS Mini deployments to replace manual data center provisioning with automated workflows to increase IT consistency and speed. This really helps your business respond quickly to new business opportunities, as Cisco UCS Director is all about unifying infrastructure management.

Finally, customers can deploy Cisco UCS Performance Manager with Cisco UCS Mini to monitor and alert IT operations personnel on potential problems in real time. Cisco UCS Performance Manager provides visibility from a single console into Cisco UCS components for performance monitoring and capacity planning. It provides data center assurance of integrated infrastructures and ties application performance to physical and virtual infrastructure performance. In essence, this allows IT staff to optimize resources and deliver better service levels to customers.

A powerful configuration – as you’ll see.

To help companies understand the full power of this solution, we’ve put together a reference architecture (available here) so you can see this configuration in action.

It uses non-persistent virtual desktop infrastructure (VDI) desktops with Citrix XenDesktop and remote desktop service (RDS) server desktops using Citrix XenApp on a four-blade Cisco UCS Mini platform combined with a Nimble Storage system.

This is the first Citrix VDI reference architecture with Cisco UCS Mini that offers versatility for deploying to a remote or branch office or directly into the data center as compact, self-contained solution. And the Nimble CS300 array makes efficient use of low-cost SATA drives combined with high performing SSDs for a hybrid storage solution that is ideally suited for VDI.

The reference architecture also shows how the solution can easily be scaled up, with increased user density gained by adding blades incrementally on an as-needed basis. In fact, the testing shows that this configuration provides an excellent virtual desktop end-user experience for 500 mixed-use-case sessions. And it can be achieved at a highly competitive price.

Both Microsoft Windows 7 VDI desktops (300 users) and Microsoft Server 2012 RDS servers (200 users) were deployed, demonstrating the flexibility of the solution.

The testing conducted consisted of single-server and multiple-server scalability tests, with a phased process.

  • Single-server testing: This test validated single-server scalability under a maximum recommended load for both RDS and VDI workload scenarios. It also validated a given density level for a single Cisco UCS blade, with the maximum recommended density level of CPU utilization between 90-95%.
  • Full-scale testing: This test determined the workload mix and validated multiple-server scalability. First, a ratio of RDS (40%) to VDI (60%) workloads was defined based on the earlier single-server scalability results. In subsequent testing, the solution was examined using that mixed workload on multiple blades for a user density of 500 sessions. By configuring a mixed workload across all blades, the solution was validated in a diverse, efficient manner. This testing revealed the most cost-effective overall configuration, especially for sites with a smaller number of users requiring different use cases.
Components VDI: Non-Persistent Desktops

(Hosted Virtual Desktops)

XenDesktop 7.6 RDSH:  Server Sessions

(Hosted Shared Desktops)

XenApp 7.6 Virtual Machine Disk OSMicrosoft Windows 7 SP1 32-bitMicrosoft Windows Server 2012Virtual CPU amount1 vCPU5 vCPUMemory amount1.5 GB (reserve all guest memory)16 GB (reserve all guest memory)Master Image Disk Size24 GB (dynamic PVS vDisk)40 GB (dynamic PVS vDisk)Citrix PVS Write Cache

Disk size

RAM cache size4 GB

64 MB30 GB

1 GBNetwork Adapter1x 10GB VMXNET3 (VDI vLAN)1x 10GB VMXNET3 (VDI vLAN)Additional softwareMicrosoft Office 2010Microsoft Office 2010Test workloadLogin VSI 3.7 MediumLogin VSI 3.7 MediumRecommended Max Load per blade150190

And … here are the results!

For companies that are looking for an efficient, cost-effective midsized solution, these results show how the Cisco UCS Mini with Nimble Storage and Citrix XenDesktop 7.6 can be an ideal solution.

  • Single-server testing:
    • XenApp (RDS) yielded a recommended max load of 190 users
    • XenDesktop (VDI) yielded a recommended max load of 150 users

The four-blade Cisco UCS Mini with Nimble Storage CS300 easily supported a total of 500 desktop sessions in a mixed VDI and RDS configuration. The user density can be doubled by adding up to four more blades to the Cisco UCS Mini chassis. The Nimble Storage CS300 can easily support this workload in both capacity and performance. As with all correctly configured reference architecture designs, host CPU was the gating factor when determining the upper limit of this solution.

In addition, the testing also showed the power of these configurations, with benefits such as:

  • Adaptive performance: Performance adapts to boot storms and I/O spikes because the flash cache is populated dynamically.
  • Cost-effective capacity: Inline compression, high-capacity disk, and zero-copy cloning all deliver capacity reductions of up to 75 percent.
  • Business continuity: High availability and integrated data protection reduces downtime for local failures and larger sidewise disasters.
  • Transparent scaling: Performance and capacity can easily be scaled independently and without downtime.

But wait, there’s more!

This configuration is also the first design of Cisco and Citrix products that incorporates the Citrix Provisioning Services feature ‘Cache in Device RAM with Overflow on Hard Disk.’ This new capability greatly minimizes the storage performance requirements driven from VDI workloads by reducing the data throughput and IOPS demand incurred on storage.

For instance, with this feature:

  • Target device write cache is written to RAM first. When RAM is full, the least used data is written to the storage differencing disk in 2MB chunks to accommodate newer data on RAM. Effectively, storage writes are coalesced from random to sequential.
  • The amount of RAM specified is the non-paged kernel memory that the target device will consume.

This write cache method uses VHDX differencing format; it is only available for Windows 7 and Server 2008 R2 and later, and it only applies only to non-persistent machines.

For this solution, the VHDX block format has a faster file expansion rate as compared to ‘Cache on Device Hard Drive’ cache mode. The local disk free space should be reconsidered to accommodate the streaming workload. To ensure target device reliability in high demand workload, Citrix recommends that local disk free space be larger than vDisk capacity size.

When the local disk is out of space, the target device vDisk IO goes in to a pause state waiting for more local disk free space to become available. This condition has a negative impact on workload continuity; thus, Citrix recommends allocating enough local disk free space for overflow.

The amount of RAM specified does not change the local disk free space requirement. The more RAM assigned, the more vDisk IOs temporarily saved in RAM cache before all data gets flushed back to the VHDX file. The RAM reduces the initial VHDX expansion rate.

Here are some comparison charts so you can see the differences. The XenApp (RDS) use case was tested with 200 user sessions and XenDesktop (VDI) tested 300 sessions.


Want to know more?

To learn more about the test results of the bundled solution discussed here, you can download the full white paper here:

  • Cisco UCS Mini, Nimble Storage, and Citrix XenDesktop 7.6 500-Seat, Mixed Workload on Cisco UCS B200 M3 Blade Servers: 

In addition, here are additional reference links for the products mentioned here in this blog. 

Frank Anderson has 20 years of experience working in the technology industry; of those, 17 have been spent working on Citrix products. Working at various Fortune 500 companies, Frank’s career began as a Desktop Engineer and progressed technically to a Citrix Principal Solutions Architect. These companies ranged from Healthcare to Entertainment to Electric Utilities and Technology. His current role as a Solutions Architect is focused on building Virtual Desktop and Application Solutions with Cisco Partners, such as Citrix. His responsibilities include solutions validation, strategic alliances, technical content creation, and testing/benchmarking.