vSphere Storage APIs Explained | VASA, VAAI, VAMP & VADP

VMware offers robust storage APIs that allow third-party vendors to build and innovate the vSphere platform. If you are not familiar with them, this article will explain what the vSphere Storage APIs is and introduce 4 common types of it.


By Crystal / Updated on March 8, 2023

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What is vSphere Storage APIs

VMware vSphere is a popular server virtualization software suite with a rich and powerful storage system. Many of its interactive features are provided by a set of APIs. This article will explain what is the VMware vSphere Storage APIs and present several common vSphere Storage APIs.

vmware vsphere backup

APIs refers to Application Programming Interfaces. vSphere Storage APIs is a family of APIs used by third-party hardware, software, and storage providers to develop components that enhance several vSphere features and solutions.

VMware is committed to provide robust storage APIs that allow third-party vendors to build and innovate the vSphere platform. Next, this article will introduce 4 common types of vSphere APIs.

4 Common vSphere Storage APIs

VMware provides many vSphere Storage APIs to enable different capabilities and meet different needs. This part will highlight 4 common types of it, VASA, VAAI, VAMP, and VADP.

vSphere Storage APIs for Storage Awareness (VASA)

vSphere APIs for Storage Awareness is also known as VASA, released with vSphere 5. These APIs enable communications between vCenter Server and underlying storage.


Through VASA, storage entities can inform vCenter Server about their configurations, storage health and events, enabling vCenter to recognize the storage arrays and its capabilities including RAID, native thin provisioning, and deduplication, etc. These capabilities are made visible within vCenter, which makes it easier for administrators to make decisions about how data stores should be maintained.

VASA also provides information about storage arrays to vSphere’s Profile-Driven Storage feature and Distributed Resource Scheduler (DRS), delivering VM storage requirements from vCenter Server to a storage entity. The Profile-Driven Storage feature ensures that the storage layer meets the requirements. and Storage DRS can work optimally with them.

VASA becomes essential when you work with Virtual Volumes, vSAN, vSphere APIs for I/O Filtering (VAIO), and storage VM policies.

vSphere Storage APIs for Array Integration (VAAI)

vSphere APIs for Array Integration, also known as VAAI, first introduced in vSphere 4.1. These APIs enable communications between VMware ESXi host and storage devices.


VMware VAAI include 2 components: Hardware Acceleration APIs and Array Thin Provisioning APIs.

  • Hardware Acceleration APIs help arrays to integrate with vSphere, so that vSphere can offload certain storage operations to the array. This integration significantly reduces CPU overhead on the host.
  • Array Thin Provisioning APIs help to monitor space use on thin-provisioned storage arrays to prevent out-of-space conditions, and to perform space reclamation.

VMware VAAI is to help storage vendors provide hardware assistance to speed up VMware I/O operations that are more efficiently accomplished in the storage hardware.

vSphere Storage APIs for Multipathing (VAMP)

vSphere APIs for Multipathing, also known as VAMP, enable VMware to control I/O path selection in a host to storage devices.

The VAMP is embedded in the VMKernel in the name of Pluggable Storage Architecture (PSA). The PSA acts as a base for two storage plugins namely VMware’s Native Multipathing Plug-in (NMP) and Multipathing Plug-in (MPP). NMP has additional sub-plugins namely Storage Array Type Plug-in (SATP) and Path Selection Plug-ins (PSP). All these plugins together make up VAMP.


These APIs allow storage partners to create and deliver multipathing and load-balancing plug-ins that are optimized for each array. Plug-ins communicate with storage arrays and determine the best path selection strategy to increase I/O performance and reliability from the ESXi host to the storage array.

VMware vSphere Storage APIs – Data Protection (VADP)

VMware vSphere Storage APIs – Data Protection, also known as vStorage APIs for Data Protection or VADP, is the next generation of VMware’s data protection framework originally introduced in vSphere 4.0 that enables backup products to do centralized, efficient, off-host LAN free backup of vSphere virtual machines.


A backup product using VMware VADP can backup vSphere virtual machines from a central backup server or virtual machine without requiring backup agents or requiring backup processing to be done inside each guest virtual machine on the ESX host. This offloads backup processing from ESX hosts and reduces costs by allowing each ESX host to run more virtual machines.

VMware VADP leverages the snapshot capabilities of VMware vSphere to enable backup across SAN without requiring downtime for virtual machines. As a result, backups can be performed non-disruptively at any time of the day without requiring extended backup windows and the downtime to applications and users associated with backup windows.

VMware vSphere Storage APIs – Data Protection (VADP) is supported on every license level of vSphere. Next, I will introduce an efficient third-party software that based on VMware VADP.

A VMware vSphere Storage APIs – Data Protection based software

As VMware deprecated vSphere Data Protection (VDP) and focus its investments on VMware vSphere Storage APIs, customers may need a third-party software to replace deprecated VDP and provide ESXi virtual machine protection. However, due to the limitation of not supporting vStorage APIs, some third-party software may not support the backup of VMs on free VMware ESXi.

In this regard, you can try the free VMware backup software AOMEI Cyber Backup which supports both paid and free versions of VMware ESXi.

Agentless Backup: create complete and independent image-level backup for VMware ESXi and Hyper-V VMs.
Support Free ESXi: AOMEI Cyber Backup support both paid and free versions of VMware ESXi.
Multiple Storage Destinations: backup to local drive, or network destinations like Windows share or NAS.
Automated Execution: create backup schedules to automate backups daily, weekly, monthly.

AOMEI Cyber Backup

AOMEI Cyber Backup supports VMware ESXi 6.0 and later versions. Next, I will demonstrate how to backup and restore multiple ESXi VMs via AOMEI Cyber Backup. You can click the following button to download and use AOMEI Cyber Backup Free Edition with no time limit.

Download FreewareVMware ESXi & Hyper-V
Secure Download

*You can choose to install this VM backup software on either Windows or Linux system.

5 steps to backup and restore multiple VMware ESXi VMs

1. Bind Devices: Access to AOMEI Cyber Backup web client, navigate to Source Device > VMware > + Add VMware Device to Add vCenter or Standalone ESXi host. And then click > Bind Device.

add vmware esxi device

2. Create Backup Task: Navigate to Backup Task > + Create New Task, and select VMware ESXi Backup as the Backup Type.

VMware ESXi backup

3. Set Task Name, Device, Target, Schedule, and Cleanup as needed.

  • Task Name: you can change the task name or use the default name with an ordinal.
  • Device: select VMs on the host to back up.

Select virtual machines

  • Target: select to back up to a local path, or to a network path like NAS.
  • Schedule (optional): perform full, differential, or incremental backup, and automate execution according to the frequency you specified.

Backup schedule type

4. Run Backup: Click Start Backup and select Add the schedule and start backup now, or Add the schedule only.

Start Backup

Created backup tasks will be listed and monitored separately, for restoring, progress checking and schedule changing.

5. Restore from backup: select the backup task and click > Restore to open the wizard, select the target VM and Restore to original location option, click Start Restore.

Or you can navigate to Backup Management > History Versions, all restore points of the VMs will be clearly listed for selection.

Restire from backup task

While the Free Edition covers most VM backup need, you can also upgrade to Premium Edition to enjoy more:
Backup cleanup: configure a retention policy to auto delete old backup files and save storage space.
Batch VM backup & restore: batch backup and restore large numbers of VMs managed by vCenter Server or on standalone ESXi hosts.
Restore to new location: create a new VM in the same or another datastore/host directly from the backup to perform out-of-spacre recovery, saves the trouble of re-configuring the new VM.

Restore to new location


vSphere Storage APIs provide incredible extended functionality to the virtual storage system. This article briefly introduced what it is and presented 4 common types of vSphere Storage APIs, including VASA, VAAI, VAMP and VADP.

VADP is designed to replace the deprecated official backup software VMware Data Protection (VDP). Therefore, you may need to migrate your backup schedules to a reliable third-party software. You can try AOMEI Cyber Backup, a simple, flexible free VM backup solution that enables you to centrally manage and automate the backup and restore of multiple VMware ESXi or Hyper-V VMs.

Crystal · Editor
Crystal is an editor from AOMEI Technology. She mainly writes articles about virtual machine. She is a positive young lady likes to share articles with peolpe. Off work she loves travelling and cooking which is wonderful for life.