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vSphere APIs for I/O Filtering (VAIO) Program

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What is vSphere APIs for IO Filtering (VAIO)

VAIO is a Framework that enables third parties (Partners) to develop filters that run in ESXi and can intercept any IO requests from a guest operating system to a virtual disk. An IO will not be issued or committed to disk without being processed by IO Filters created by 3rd parties.

Filters execute inside ESXi and not in a VM. In addition, the VAIO Framework provides centralized installation and upgrade.

The first release of vSphere APIs for IO Filtering (ESXi 6.0 Update 1) will only support and certify the Caching and Replication use cases. VMware will not certify VAIO solutions attempting to support other use cases at this time.

Caching - Will significantly increase the IOPS available, reduce latency, and increase hardware utilization rates.

Replication - Will allow the user to create VM granular replication policies for use in DR and other scenarios (ie. Snapshot)

Note: This program does entail a vetting process and based on the answers to the questionnaire below, partner solutions may or may not qualify for this program.

How IO Filtering Works

IO request moving between the guest operating system (Initiator), located in the Virtual Machine Monitor(VMM), and a virtual disk (Consumer) are filtered through a series of two IO Filters (per disk), one filter per filter class, invoked in filter class order. For example, a replication filter executes before a cache filter. Once the IO request has been filtered by all the filters for the particular disk, the IO request moves on to its destination, either the VM or the virtual disk.

Partner will develop IO Filter plug-ins to provide filtering virtual machines. Each IO Filter registers a set of callbacks with the Filter Framework, pertaining to different disk operations. If a filter fails an operation, only the filters prior to it are informed of the failure.

Any filter can complete, fail, pass, or defer an IO request. A filter will defer an IO if the filter has to do a blocking operation like sending the data over the network, but wants to allow further IOs to get processed as well. If a filter performs a blocking operation during the regular IO processing path, it would affect the IOPS of the virtual disk, since we wouldn't be processing any further IOs until the blocking operation completes. If the filter defers an IO request, the Filter Framework will not pass the request to subsequent filters in the class order until the filter completes the request and notifies the Filter Framework that the IO may proceed.

VAIO Overview Architecture

Program Overview

The vSphere APIs for I/O Filtering Certification program provides tools and development resources designed to enable TAP partners to get their developed Filter class tested against vSphere and obtain official VMware certification and support.
Upon successful completion of Filter IO certification and digitally signed by VMware,  the products will be listed in the VMware Compatibility Guide. Partners will also be provided with a VMware ReadyTM logo, which can be used in their marketing and sales efforts of the certified products.
As a member of this program, you'll be provided with up to date product communications on VMware vSphere release dates, certification policies, and product features.

Key Benefits

Development Resources

Program access includes the tools and resources needed during the development and release phases. 
  • Access to the Program Documents, Development Kit, pertinent Development Documentation, and Workbench for partner Filter class development
  • Certification
The program includes access to the program's Certification Kit, which allows partners to test the reliability and stability of their code. VMware verifies that the test results support the partner during the certification process. 
  • VMware Compatibility Guide (VCG) posting
Upon successful certification, the partner works with Ecosystem Engineering to update the VMware Compatibility Guide entry on Once the partner's products are certified and digitally singed by VMware under the terms of the program, the partner may use the VMware Ready™ logo in product collateral.
  • Program communication
Ongoing program communications pertaining to updated certification kit and milestones.
  • vSphere Installation Bundle Suite (VIB)

   Used to package the Partner Developed Filter Class so that can be installed on ESXi

  • Access to Maintenance Releases
Membership in this program is ongoing, and partners are entitled to vSphere and vCenter update releases as well as development and certification kit refreshes for the duration of their participation in the program. Additionally, the program allows for access to early versions of vSphere for the purpose of developing and testing.

Program Requirements

This program is governed by the following requirements:
  • TAP Elite or Global status
  • Partner Solution vetting (approval required). Please fill out the questionnaire below and send it to
  • VMware program agreement signature
  • Adherence to product support requirements as documented in vSphere APIs for I/O Filtering Program Guide document.
  • TSANet membership and an entry in the VMware custom TSANet portal
  • General support on VMware vSphere features is purchased separately

Product Versions Supported

This program supports the following product versions:


6.0U1, 6.0U2, 6.5.x, 6.7.x

Target Audience

  • Storage and Server partners

Related Programs and Services

  • Engineering Services Development Consulting Program

VMware Ready Category

Software Products

Documentation and Reference