The New Nutanix Workload Sizer is better than my VDI Calculator, but…

For many years my VDI Calculator has been the source of truth for many VDI deployments, and still is. The calculator went through many iterations and had many features included overtime to support Horizon View and XenDesktop deployments to its full extent, including some very specialized features such as the use of Content Based Read Cache, Dedicated Replica Datastore, 3D Graphics and others. On average the VDI calculator helps 2,272 architects, system administrators and consultants every month. That’s a staggering number and I feel very proud providing a free tool that many find very useful and love.




Over the years, Nutanix developed an extensive depth and breadth of internal intelligence on how to size and scope workloads including VDI deployments and virtualized business applications. This knowledge is now being made available through the Nutanix Workload Sizer, part of a comprehensive service delivery platform from Nutanix Global Services. The Nutanix Workload Sizer helps partners size and design Nutanix clusters with both ease and confidence.

Over 500 Nutanix partners have already been through the Workload Sizer Tool Launch Webinars. As this video conveys, the Workload Sizer Tool was developed by Nutanix Global Services (GSO) with the same type of simplicity and elegance that Nutanix strives to imbue in all of our products, tools and supporting documentation.If you are a Nutanix partner I strongly recommend reading Steve Kaplan’s article, Nutanix Workload Sizer: Designing web-scale datacenters just got easier.

To get free access to the Nutanix Workload Size click here.


Whilst the Nutanix Workload Sizer is a general purpose workload sizer, including popular applications like Exchange, SQL Server, and Server Virtualization, the sizer is actually very good for VDI workloads; going into details about provisioning type, user date capacity, vGPU, de-duplication, compression and others. I recommend Nutanix partners to utilize the Nutanix Workload Sizer to generate detailed reports that include a fully documented pricing and cost per desktop summary.






You may still use the  calculator for non-Nutanix VDI workloads or VDI deployments that require a more granular sizing. Using the VDI calculator it is possible to be very specific about how you want to deploy the solution and how you want it to behave. Some of the unique features offered in the VDI calculator are applicable also to Nutanix deployments, while other features are specific to other types of storage solutions:


  • Average vCPU MHz – Average CPU utilization per desktop. If not known leave, as Default.
  • Refresh OS disk on logoff at – How often desktops are refreshed after use (Affect only Linked Clones)
  • Persistent Disk (UDD) – Size of Persistent Disks (Affect only Linked Clones)
  • Disposable Disk – Size of Disposable Disks (Affect only Linked Clones)
  • Number of Desktop Pools – Maximum of 512 desktops is allowed per pool. It will show an error (ERR) if the number of desktops pools is too small to support the number of desktops. Read more at A review of VMware View 4.5 Limits and Maximums.
  • Number of Snapshots per Pool – Recommended to set two snapshots per desktop pool to accommodate recompose operations. This number affects the calculation of the replica datasore.
  • Desktop State when Not in use – Defines host CPU consumption and storage footprint for VMs in suspended mode or powered off when not in use.
  • Cores per Host – Total number of cores per host. Not necessarily more cores are always better.
  • % Host Shared Memory (TPS) – Define the amount of Transparent Page Sharing per host. This number changes according to GuestOS type, applications in execution, and helps to calculate the total amount of memory required per host.
  • % VM Memory Reservation – Increasing memory reservation reduces VM swap file. This setting plays a key factor on storage savings. Read more at Pagefiles and VDI. Not so simple.
  • Hypervisor Memory Overhead – Amount of RAM reserved for hypervisor kernel operations.
  • VM Memory Overhead – This field is automatically calculated based on several external factors.
  • Connection Server HA (n+1) – Calculate redundant connection brokers in a N+1 scenario.
  • Number of Displays – Affect VM Memory Overhead
  • Display Resolution – Affect VM Memory Overhead
  • Connection Type – (Only for RDP connections) Define the scalability of connection brokers. Tunneled connections decrease the amount of connections per broker.
  • External Users – Number of users simultaneously connecting through View Security Servers.
  • Dedicated Replica Datastore – View 4.5 introduced the ability to dedicate datastores for read IO intensive replicas.  The use of Dedicated Replica Datastore helps to reduce the amount of storage required and allow assignment of tier 1 storage for replica disks. Read more at VMware View 4.5 Linked Cloning explained.
  • Place VM .vswp on Local Storage – Placement of VM .vswp files on local storage help in reducing amount of shared storage required. Read more at Save [VDI] Storage using VM Swap File Host Placement.
  • RAID Type – RAID type impact on performance. Select the appropriate RAID group for the Linked Clone datastores.
  • %Read – %Write – Define IO pattern for IO operations per VM. This settings impact directly on the number of IOs calculated.
  • VAAI – vStorage API for Array Integration enabled for storage arrays providing ATS mechanisms.
  • Caching – Intelligent arrays make use of DRAM and/or SSD memory to store most accessed blocks in memory. Memory stored in memory do not require backend spindle access, therefore reducing the total requirements on the backend. This is a powerful option but should be used with caution. Normally is not possible to know the caching ratio until a project pilot is done.



  • If you are sizing for Nutanix deployments follow this path
    • If you are scoping an opportunity you should use the Nutanix Workload Sizer as your source of truth.
    • If you are beginner in sizing VDI deployments you should use the Nutanix Workload Sizer as your source of truth.
    • If you are architecting a detailed VDI solution and is an advanced user in sizing VDI deployments my recommendation is to use my VDI calculator and follow-up with a Nutanix Workload Sizer verification. One of the major differences is that while using the VDI calculator you must define Nutanix node types upfront, when using the Nutanix Workload Sizer the node types will be provided to you as a result of the calculation.
  • If you NOT sizing for Nutanix deployments follow this path
    • Utilize the VDI Calculator as your source of truth.


To access the Nutanix Workload Size click here.

To access the VDI calculator click here.



This article was first published by Andre Leibovici (@andreleibovici) at

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