So this is the Million Dollar Question, right? You, along with the executives sponsoring your particular VDI project wanna know: How many desktops can I run on that blade? It’s funny how such an “it depends” question becomes a benchmark for various vendors blades, including said vendor here.
Well, for the purpose of this discussion series, the goal here is not to reach some maximum number by spending hours in the lab tweaking various knobs and dials of the underlying infrastructure. The goal of this overall series is to see what happens to the number of sessions as we change various aspects of the compute: CPU Speed/Cores, Memory Speed and capacity. Our series posts are as follows:
You are Invited! If you’ve been enjoying our blog series, please join us for a free webinar discussing the VDI Missing Questions, with Doron, Shawn and myself (Jason)! Access the webinar here!
But for the purpose of this question, let’s look simply at the scaling numbers at the appropriate amount of RAM for the the VDI count we will achieve (e.g. no memory overcommit) and maximum allowed memory speed (1600MHz).
As Doron already revealed in question 1, we did find some maximum numbers in our test environment. Other than the customized Cisco ESX build on the hosts, and tuning our Windows 7 template per VMware’s View Optimization Guide for Windows 7, the VMware View 5.1.1 environment was a fairly default build out designed for simplicity of testing, not massive scale. We kept unlogged VMs in reserve like you would in the real world to facilitate the ability for users to login in quickly…yes that may affect some theoretical maximum number you could get out of the system, but again…not the goal.
And the overall test results look a little something like this:
E5-2643 Virtual Desktops
E5-2665 Virtual Desktops
As explained in Question 1, cores really do matter…but even then, surprisingly the two CPUs are neck and neck in the race until around 40 VM mark. Then the 2 vCPU desktops on the quad core CPU really take a turn for the worse:
When a VM has two (or more) vCPUs, the hypervisor must find two (or more) physical cores to plant the VM on for execution within a fairly strict timeframe to keep that VM’s multiple vCPUs in sync.
MULTIPLE vCPU VMS ARE NOT FREE!
Multiple vCPUs create a constraint that takes time for the hypervisor to sort out every time it makes a scheduling decision, not to mention you simply have more cores allocated for hypervisor to schedule for the same number of sessions: DOUBLE that of the one vCPU VM. Only way to fix this issue is with more cores.
That said: the 2 vCPU VMs continue to scale consistently on the E5-2665 with its double core count to the E5-2643. At around the 85 session mark, the even the E5-2665 can no longer provide a consistent experience with 2vCPU VDI sessions running. I’ll stop here and jump off that soap box…we’ll dig more into the multiple vCPU virtual desktop configuration in a later question (hint hint hint)…
Now let’s take a look at the more traditional VDI desktop: the 1 vCPU VM:
With the quad-core E5-2643, performance holds strong until around the 60 session mark, then latency quickly builds as the 4000ms threshold is hit at 81 sessions. But look at the trooper that the E5-2665 is though! Follow its 1 vCPU scaling line in the chart and all those cores show a very consistent latency line up to around the 100 session mark, where then it becomes somewhat less consistent to the 4000ms VSImax of 130. 130 responsive systems on a single server! I remember when it was awesome to get 15 or so systems going on a dual socket box 10 or so years ago, and we are at 10x the quantity today!
Let’s say you want to impose harsher limits to your environment. You’ve got a pool of users that are a bit more sensitive to response time than others (like your executive sponsors!). 4000ms response time may be too much and you want to halve that to 2000ms. According to our test scenario, the E5-2665 can STILL sustain around 100 sessions before the scaling becomes a bit more erratic in this workload simulation.
Logic would suggest half the response time may mean half the sessions, but that simply isn’t the case as shown here. We reach Point of Chaos (POC!) where there is very inconsistent response times and behaviors as we continue to add sessions. In other words: It does not take many more desktop sessions in a well running environment that is close to the “compute cliff” before the latency doubles and your end users are not happy. But on the plus side, and assuming storage I/O latency isn’t an issue, our testing shows that you do not need to drop that many sessions from each individual server in your cluster to rapidly recover session response time as well.
So in conclusion, the E5-2643, with its high clock speed and lower core count, is best suited for smaller deployments of less than 80 desktops per blade. The E5-2665, with its moderate clock speed and higher core count, is best suited for larger deployments of greater than 100 desktops per blade.
Next up…what is the minimum amount of normalized CPU SPEC does a virtual desktop need?
Tags: citrix, cpu, UCS, vdi, virtual desktop, virtualization, VMware, vxi
Can 1 +1 really = 3 (or more)? Consider the opportunity presented by the thoughtful convergence of BYOD and virtual desktop technologies.
BYOD is one of the most important trends in education technology today. However, many BYOD initiatives are limited to providing personal devices with basic network connectivity via the campus Wi-Fi network. Traditional virtual desktops (VDI) are not new in education. Historically, VDI has allowed the delivery of non-persistent desktops, primarily to thin clients.
Through the Cisco Unified Workspace for Education, schools, colleges and universities can now provide next generation education workspaces that are virtual, social, mobile and collaborative. The Cisco Unified Workspace for Education integrates the Cisco BYOD and Virtualization Experience Infrastructure (VXI) Smart Solutions to provide students, faculty, and staff with the flexibility of using any device to access any information, any application, and any expertise—from anywhere.
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Tags: byod, education, higher education, unified workspace, vdi, vxi
Welcome back as we continue to dive deeper into advanced CPU (Central Processing Unit -- I had a “tech writer” change a document on me one time, he assumed at this day in age that people still needed to have the CPU acronym translated.. but I digress) and Memory concepts in the land of VDI. Last week Doron answered our first question and told us about Core Count vs. Core Speed for scalable VDI. This week we will focus specifically on Core Speed, bursting and introduce you to a potentially new subject called “SPEC Blend/Core” for high performance VDI. If you are just finding this blog post for the first time, I encourage you to check out the Introduction from Tony as it will help set the stage for our discussion. Here is the full table of contents:
- Introduction – VDI – The Questions you didn’t ask (but really should)
- VDI “The Missing Questions” #1: Core Count vs. Core Speed
- VDI “The Missing Questions” #2: Core Speed Scaling (Burst) YOU ARE HERE!
- VDI “The Missing Questions” #3: Realistic Virtual Desktop Limits
- VDI “The Missing Questions” #4: How much SPECint is enough
- VDI “The Missing Questions” #5: How does 1vCPU scale compared to 2vCPU’s?
- VDI “The Missing Questions” #6: What do you really gain from a 2vCPU virtual desktop?
- VDI “The Missing Questions” #7: How memory bus speed affects scale
- VDI “The Missing Questions” #8: How does memory density affect VDI scalability?
- VDI “The Missing Questions” #9: How many storage IOPs?
You are Invited! If you’ve been enjoying our blog series, please join us for a free webinar discussing the VDI Missing Questions, with Tony, Doron, Shawn and Jason! Access the webinar here!
VM’s are only as fast as their individual cores! Lets look at what this statement means. Example: Assume we have a 1GHz x 4 core processor (hey, it makes math easy for me). When we carve up a server VM or in this case a VM to be used for VDI, we can’t just give it 2 vCPU’s and say it’s got a 2GHz processor. The reality is that it has a dual 1GHz processor. This becomes an important concept in VDI when you are considering the quantity and QUALITY of vCPU’s you allocate to a Virtual Machine and ultimately the end user applications efficiency and the overall scalability of the server platform. This is not a Uni-processor vs. Multi-processor application discussion. We could easily have a very long discussion and debate on the in’s and out’s of application level efficiencies and the Operating Systems ability (and sometimes inability) to properly manage multiple CPU’s. We are going to expand upon the two CPU’s we tested and dig into per core performance.
CPU Burst vs. CPU Reservation. Let’s play around with our example 1GHz x 4 Core Processor a bit more. If we take this single processor and deploy 8 single vCPU desktops on it we will have a 500MHz CPU reservation per VM. The calculation for that is simple 1GHz x 4 Cores = 4,000MHz / 8 total VM’s = 500MHz/VM Reservation. So the Reservation is simply the average amount of CPU that is available to each VM (assuming everything is prioritized equally). But our Burst is different. Our Burst represents the maximum amount of CPU Core that any one VM could ever utilize. In this example, the Burst per VM is equivalent to 1GHz.
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Tags: Burst, Cisco, desktop virtualization, performances, Speed, vdi
Choosing the right compute platform for your VDI environment requires both science and art. You have to balance CPU and memory characteristics against your expected workload profile and your desired density. At the end of the day, VDI has to meet some cost criteria in order to go from a fun science project to a funded program in your company. That means you can’t just throw the top bin CPU at the problem; you have to pick the right CPU. This is further complicated by the fact that there is not one CPU that is ideal for all VDI workloads. There is no magical bill of materials at the end of this series of blogs, but we will attempt to make your VDI decisions based more on science than art.
Strength in numbers? Or strength in speed? As Tony said in his introduction, we had several involved questions related to VDI that we honestly couldn’t answer… so we decided to start testing. This will be a series of blogs that attempts to answer practical questions like “when is processor A better than processor B?” And of course you then have to ask “when is processor B better than processer A?” In this first installment in the series, I will tackle the question of whether the number of cores or the core speed is more important when the goal is to achieve the best desktop density per host. Here is a handy guide to the other posts in this series:
The usual suspects. Throughout this series, we will focus on two processors. We picked them because they are popular and cost effective, yet quite different from each other. They are not top bin processors. Take a look at the table below for a comparison.
Note: Prices in this table are recommended prices published by Intel at http://ark.intel.com and may vary from actual prices you pay for each processor. The SPEC performance numbers are an average of SPEC results published by many OEMs (at http://www.spec.org/) across many platforms. These are not Cisco-specific SPEC numbers.
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Tags: citrix, cpu, UCS, vdi, virtual desktop, virtualization, VMware, vxi
Making sure your users don’t go to sleep (or worse) waiting to log-on
Hi Everyone! I am the team lead Technical Marketing Engineer for Cisco Virtual Desktop Infrastructure (VDI) solutions on UCS and Nexus. While I have done some blogging in my time – this is my first blog for Cisco. I have been in this space for over 22 years, before “virtualization” was called that, working with published applications and published desktops (MetaFrame and early RDP.)
With the Citrix and EMC teams, I have been focused for the past few months on validating what I think is a really exciting solution -- even if I say so myself. So recently not much time for blogging I am afraid.
Over the last couple of years we have seen desktop virtualization, specifically Hosted Virtual Desktops (HVD,) become increasingly more mainstream -- but today we are really experiencing an upsurge of deployments -- and not just pilots -- but full blown multi-thousand seat deployments.
As you are probably aware the worst nightmare is that you deploy the solution and the users don’t adopt it because it doesn’t provide them the user experience they need or want.
One of the key requirements for success is an infrastructure that won’t just provide the right experience for the first few hundred users -- but that will scale linearly as you grow into the many thousands.
You can rely on Cisco Validated Designs to deliver for you! We use real world test scenarios to insure that you can implement our designs in your environment and be successful.
The keys to a successful deployment of a large scale HVD environment start with:
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Tags: Cisco, citrix, data center, desktop virtualization, EMC, hvd, nexus, UVCS, vdi