Feature Brief: VMware Cloud Sizer


VMware Cloud Sizer is a free online service that helps customers assess workloads and estimate required resources to run virtual machines in VMware Cloud on AWS environment efficiently.  It is a vital tool for capacity estimations used for migration project planning and can also provide insights for greenfield deployment and extension of the existing VMware Cloud environment.

Sizer helps customers to estimate the number of hosts required to run their virtual machines (VMs) and currently supporting VMware Cloud on AWS.

Depending on your requirements VMware Cloud Sizer provides customers rough estimates based on industry averages or can be used for more accurate information using performance data of customer’s workloads.

Once a customer gets estimates from the VMware Cloud Sizer, they could work with the VMware Cloud Economics team to evaluate the financial aspects of the migration and build TCO.

How it Works

VMware Cloud Sizer service is available at the https://vmc.vmware.com/sizer URL and you can use it straight away. You would need to log in to your Customer Connect account if you would like to save your project for future reference. It could be also found at the VMware Cloud Services console or accessed from the "Launchpad" page of VMware Cloud on AWS

New: VMware Cloud Sizer Advanced options were renamed to Advanced Sizer (Non-VDI) and Advanced Sizer (VDI) to reflect different user scenarios covered by each of the sizer types and simplify sizing exercises.

There is now also segregation between New and Existing SDDC use cases.

VMware Cloud Sizer Main Page

Sizer Hardware Support

In addition to the i3 and i3en instance types, VMware Cloud Sizer now supports modern i4i instances for every sizing exercise including Quick and Advanced Workload based sizers and Host Based sizing. Please note that the i3 instance type of VMware Cloud on AWS reached the end of the sale on February 1st, 2023. Check the VMware blog Announcement of the end of sale, end of support and end of life timeline of the i3.metal instance type of VMware Cloud on AWS for more details.

If you would like to consider using external storage then you should utilize Advanced Sizer  (Non-VDI) which supports VMware Cloud Flex Storage, and FSx NetApp ONTAP for VMware Cloud on AWS storage provider.

New: Quick Sizer now leverages the latest logic and API and also supports external storage using vSAN+VMware Cloud Flex Storage as a default option.

Data Sources

You can use different sources of data for workload-based sizing, and this can affect the accuracy of the results provided by VMware Cloud Sizer.

Manual input is the simplest method that could be used for greenfield deployment or if you don’t have a view of the workload baseline.

Workload data collection for sizing purposes allows to use on-premises data and get a good sizing estimate based on real-life use cases. VMware Cloud Sizer supports data collected by RVTools or Live Optics.


RVTools is a free Windows .Net application that connects directly to a vSphere environment using vCenter API and exports a current snapshot of the inventory. RVTools generates an Excel sheet file that contains the details on every VM in the environment. By uploading the file, you can get more accurate sizing because the sizer contains details of every VM configuration. It does not include storage performance requirements, relies on a single data collection point, and might miss peak CPU and memory demand for VMs which could affect actual workload requirements.

Live Optics

Live Optics is a free service from Dell EMC that can capture workload utilization over a designated period. The tool uses agent-driven data collections of any workload and can run for a given duration. Live Optics also includes storage performance data and can be particularly helpful when dealing with highly demanding workloads. It is similar to RVTools but slightly better as you can accurately account for performance and capacity.

Sizing Options

Based on your requirements you can use Quick Sizer which is helpful for rough estimation and if you would like to use only one workload type. If you need more accurate results, you should consider Advanced Sizer options, which can use several workload types and allow you to fine-tune your inputs.

Alternatively, you can use Host Based Sizer to get a recommendation on how many free resources would be available for you to use.

New: The latest September release of the Sizer introduces Cluster Conversion Estimation workflow, which allows you to understand the number of ESXi hosts required after converting the cluster to new host instances.

Quick Sizer

This option provides a rough estimate using minimal information. Quick sizing is appropriate for initial sizing and uses default assumptions that might not fit the customer’s scenario and it is recommended to use Advanced Sizer options to get accurate results. Quick Sizer only supports manual input based on the number of VMs and average compute and storage requirements. If you are not sure of the average values, you can enter the total compute and storage requirements for your workloads.

New: Quick Sizer now supports external VMware Cloud Flex storage and uses it for virtual machines placement in conjunction with vSAN. Together with individual workload placement, this provides more accurate recommendations.

Quick Sizer

Quick Sizer allows you to input basic parameters:

  • Workload Type – General Purpose VMs, Oracle or Microsoft SQL DB and VDI Desktops acting as a quick preset for the sizer and affecting IO pattern.
  • Number of VMs and their configuration (vCPU, vRAM, Storage)
  • Enable Stretched Clusters which represent the deployment model where hosts are in different geographical locations (Availability Zones)
  • vCPU/pCore – CPU Overcommit factor
  • SDDC Host Type – i4i (default), i3 or i3en

Advanced Sizer (Non-VDI)

Advanced Sizer New is now called Advanced Sizer (Non-VDI) to reflect that it caters to server workloads. Using this type of sizer allows you to provide manual inputs for server virtual machines and fine-tune parameters. It also supports data collection from RVTools or Live Optics. You can also use more than one workload profile which provides a more granular approach and allows you to make better assumptions on required resources. If required, you can duplicate the existing workload profile to avoid manual inputs for additional VMs.

Sizer looks at each workload individually allowing to find VMs unsuitable for the cloud infrastructure and give a more accurate recommendation by providing individual workload placement.

Manual settings inputs on the Basic workload tab are the same as those in Quick Sizer except for the additional IOPs field for VMs. Workload Type preset selection affects storage IO consideration for the calculation.

Advanced Sizer (Non-VDI) manual inputs

The big change is hidden under the Additional tab which allows you to change default values to fine-tune workload parameters:

  • CPU and memory utilization
  • Target RAM ratio to define memory overcommit
  • Dedup/Compression Ratio
  • Workload I/O Access pattern, Size and Read/Write Ratio

Advanced Sizer Additional Settings

Profile settings allow you to tune parameters for specific workloads which provides a more granular approach for VMs placement. You can select host instance type for each workload profile. Storage preference settings allow to select vSAN, External or both storage types to place VMs from the profile. External storage selection supports VMware Cloud Flex and Amazon FSx for NetApp ONTAP.

New: Essential settings are now located on the main page of the workload profile making it more transparent and easy to use. Profile settings window contains separate cluster and Fault Tolerance policy options which can be used if you need to isolate specific types of VMs from other types of workloads and would like to use different FTT/FTM (e.g. cluster required to run DB VMs exclusively)

Profile Settings

Another difference from a Quick Sizer is a Global Settings window which allows you to modify settings applicable to all workload profiles. You can change vCenter SDDC Appliance size, enable stretched cluster, adjust Fault Tolerance policy (FTT and FTM) and specify reserved CPU cores value and Hyper-threading weight (this is applicable for i4i and i3en only). You can also exclude management overhead for sizing in Global settings removing SDDC vCenter and other service workloads from the calculation which is useful for existing SDDC use cases.

Advanced Sizer (Non-VDI) global settings

In addition to that Advanced Sizer allows you to select Add-on integrated services that would add a footprint to the capacity consumed by the system workloads. VMware HCX allows you to extend On-Premises environments to the cloud for seamless application migration. Cloud Disaster Recovery or VMware Site Recovery enables Disaster Recovery service depending on the required balance between flexibility and cost efficiency.

    The import option allows you to use RVTools or Live Optics data collected from the customer’s environment and provides a choice to consider the power state of virtual machines to import and whether to use utilized or provisioned storage and memory.

    Import optoins

    After importing new workload profile is created with the total number of VMs, average values for vCPU, RAM and Storage per VM, and the ability to tune additional inputs on the same page.

    Advanced Sizer (Non-VDI) Data Import

    Performance metrics from the Live Optics data samples are used to determine storage recommendations for the sizer to automatically select either vSAN or External Storage for individual Virtual Machines. This is different from RVTools import where, by default, External Storage would be used unless “vSAN Only” option is selected in profile settings.

    Advanced Sizer (VDI)


    Advanced Sizer (VDI)  previously known as Advanced Sizer Classic is focused on VDI Workloads and could use both manual inputs and RVTools or Live Optics data.  Same as for non-VDI Sizer it supports several workload profiles for sizing exercise.

    New: For ease of use VDI Sizer was simplified leaving minimum configurable options and still providing relevant recommendations for end-user computing (EUC) scenarios.

    VDI Sizer manual inputs

    The Global Settings window allows you to specify SDDC appliance size (Regular or Large) or you could leave it with default Auto value.

    The workload data import process is the same as for Advanced Sizer (Non-VDI).

    VDI Sizer data import

    Due to the nature of VDI desktops, Stretched Cluster, HCX and Disaster Recovery Add-ons services are not available for such types of workloads.

    Host Based Sizer

    Host Based Sizer provides insight into available free resources based on the number of hosts and instance type in the cluster. It becomes available after signing into a VMware Cloud Services Account.

    Basic settings consider stretched cluster requirements and management overhead.

    "Additional" tab allows you to change default values used for the calculation such as Hyper-Threading (applicable only for i4i and i3en), vCPU Per Core, Target RAM Ratio and Storage efficiency and Fault tolerance policy (FTT and FTM Type)

    Host Based Sizer

    New: Cluster Conversion Estimation

    Cluster conversion workflow is a long-awaited feature that allows customers to estimate the number of hosts in the cluster after converting them to new model instances. It allows customers to make informed decisions and understand the future capacity for cluster conversion scenarios with legacy i3.metal host models. It also provides estimations for conversion of i3en.metal hosts cluster.

    Cluster Conversion Estimation uses information from the customer’s SDDC environment, meaning that Organization should have VMware Cloud on AWS service enabled and you should be logged in to VMware Cloud Console with VMware Cloud on AWS service role to run this workflow.

    It is available under the “Existing SDDC” tab on the main screen of the VMware Cloud Sizer.

    Cluster Conversion Main Page

    After reading inventory data and getting a list of supported SDDCs you need to drill down to the specific SDDC to see a list of clusters. Selecting the host instance model in the “Convert to” column runs the script on the backend which calculates current utilization, the required number of hosts after conversion and estimates the conversion time needed.

    Cluster Conversion Host Selection

    Conversion logic considers the storage utilization of the current cluster only and also takes into account 16 hosts cluster limit excluding the source cluster from conversion calculation if the target exceeds the limit. In that case the customer could consider using external storage or reducing the number of hosts in the cluster.


    After adding workload data manually or importing collected data VMware Cloud Sizer provides you online recommendations with resource breakdown and assumptions used for sizing exercise.

    Signing into the Cloud Console account of your organization allows you to save sizing inputs to the projects for future reference and share them with people across your organization.

    Each sizer type allows you to download a PDF report with complete details on input workloads, settings, and target recommendations.

    There are a few reporting enhancements available for Advanced Sizer (Non-VDI): 

    • Cluster mapping report showing workload placement at a cluster level available in CSV format. This report contains a list of clusters with virtual machine names proposed for the placement and considers datastores (require vSAN or eligible for external storage) for specific workloads. Please note that for storage recommendation sizer needs VMs performance data which is available with Live Optics data samples.
    • Unsupported workloads report showing the ineligible workloads. Recommendations from Advanced Sizer (Non-VDI) would also include information regarding outlier VMs (if any) from uploaded workload profiles that couldn’t be migrated to the cloud and should be excluded.

    If you are looking not only into hardware sizing but also need to evaluate and compare the cost of ownership (TCO) of the solution, you could request TCO for VMware Cloud on AWS based on your assumptions via email or build your own using TCO Calculator.


    New: Quick Sizer which is now utilizing the latest API logic considers external VMware Cloud Flex storage and adds it to the report and online recommendations.

    Sizer Recommendations

    Cluster Conversion Estimation report provides you with summary information on the number of hosts after conversion, NSX edges, estimated time required for conversion and assumptions used for calculations.

    Cluster Conversion Results


    API Access

    VMware Cloud Sizer supports REST API calls and offers rich functionality for tighter integration and automation for hosts and resources recommendations. API documentation could be found VMware Developer Documentation resource which contains "Getting Started" guide and detailed information regarding API calls and data structure.

    • API access requires Cloud Service Provider (CSP) authentication.
    • Total based sizing is based on input workload characteristics
    • Workload eligibility assessment allows to filter out outliers
    • Target cloud recommendation takes SDDC topology into consideration
    • Supports data import formats from RV Tools, Live Optics and VMware Aria Operations
    • Cost Optimized option to provide the ability to size based on minimum cost
    • Additional support of Google Cloud VMware Engine and VE1 hosts

    Default Sizer Values

    To provide results Sizer proceeds with user inputs (Workload type, number of virtual machines, VM configuration, etc.) and uses additional parameters (hardware server type, resource overcommitment, VMs performance, use of external storage, storage policies, DR and stretched cluster requirements, etc.) which affect required estimated capacity to run your workloads.

    These parameters can be set manually, or left with default values.

    Sizer also takes into consideration configuration maximums and SLA for VMware Cloud on AWS to provide accurate sizing. More information regarding maximums could be found on VMware Cloud on AWS Documentation and VMware Configuration Maximums resource

    • Maximum 16 hosts per cluster
    • By default, the sizer uses the Auto mode based on VMware Cloud SLA-specific managed storage policy recommendations to determine the settings that can minimize the number of hosts in the recommendation while also complying with the VMware Cloud SLA requirements
    • Stretched clusters with four hosts or fewer use No data redundancy and have Site Disaster Tolerance set to Dual Site Mirroring (FTT:0, RAID:0)
    • VM Outliers section shows the non-eligible workloads excluded from the sizing

    Quick, VDI and Host Based sizers have only a few settings that can be altered, while Advanced Sizer (Non-VID) provides more flexibility and accurate results based on your assumptions. You can see values used for calculation in "Additional Info" part of the report ("SDDC & Cluster", "Headroom & vSAN Policy" and "Sizing Assumptions" tabs).

    Workload Based Sizers

    The following default values are used to perform calculations for Quick and Advanced Sizers:


    Default Value

    CPU Headroom


    Hyper Threading Factor

    1.25 for i4i and i3en. Disabled for i3

    Memory Overcommit Factor


    CPU Utilization


    Memory Utilization


    Dedup/Compression Ratio

    1.25 for i4i and i3en, 1.5 for i3

    IO Access Pattern


    Default IO Size

    Dependent on Workload type

    Default IO Ratio

    Dependent on Workload type


    Dependent on Workload type

    Include Management VMs

    True, without add-ons (HCX, VSR, etc.)

    FTT and FTM Type


    SDDC Appliance Size


    VM Outliers Criteria

    The following logic is used to identify VMs that are not good candidates for migration and are marked as outliers in Advanced Sizer (Non-VDI):

    • VMs vCPU count should be lesser than 75 percent of total host cores * vCPU/pCore, else it is classified as an outlier
    • VMs vRAM should be lesser than 75 percent of the host RAM * Target RAM Ratio, else it is classified as an outlier
    • Storage outliers should not cross 50% limit at the cluster level

    Host Based Sizer

    The following default values are used for recommendations:

    SDDC Host Type




    Hyper-Threading Factor



    Not supported

    vCPU Per Core




    Target RAM Ratio




    Dedup/Compression Ratio




    FTT FTM Type




    CPU Headroom




    Appliance Size





    To Conclude

    VMware Cloud Sizer is an essential tool that allows customers to get a view of the required capacity of VMware Cloud on AWS based on their requirements. It provides needed sizing accuracy depending on level of workload details.

    The tool offers customers to leverage both UI and automation capabilities through API for sizing exercises.

    VMware Cloud Sizer plays an important role for Cloud Design and Migration planning, simplifying decision-making.

    To learn more you can take a look at these demos going through the details of different sizing options:




    August 22 2023

    First version

    September 21 2023

    New features of VMware Cloud Sizer 5.4

    Quick Sizer:

    • Sizing logic is updated to use the latest V5 API.
    • Default sizing with storage preference is set to vSAN + External Storage (VMware Cloud Flex Storage).

    Advanced Sizer (non-VDI):

    • Added manual mode for workload profiles
    • Simplified profile settings for host instance and storage preference

    Advanced Sizer (VDI):

    • Simplified sizing process for manual inputs and VDI workloads import

    September 27 2023

    New Cluster Conversion Estimation Workflow

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