VMware vSAN™, the market leader in Hyper-Converged Infrastructure (HCI) storage, enables low cost and high performance next-generation HCI solutions. It converges traditional IT infrastructure silos onto industry-standard servers and virtualizes physical infrastructure to help customers easily evolve their infrastructure without risk and improve TCO over traditional resource silos. vSAN provides both enterprise-class scale and performance supporting a wide variety of use cases and businesses of all types and sizes.

One of the popular use cases for VMware vSAN is Business-Critical Applications (BCA). BCA are frequently deployed on cluster aware filesystems that use shared virtual disks(vmdk).

By default, a vSAN datastore helps ensure data integrity by preventing multiple virtual machines from writing to the same virtual disks, which poses a challenge for sharing disks. The multi-writer option enables multiple virtual machines from same or different ESXi host to simultaneous access a virtual disk on a vSAN datastore. This option helps provisioning storage for highly available applications that use a cluster filesystem.

This feature has been available for VMFS datastore for quite few years and supported with vSAN since early days with the release of this KB 2121181. The following diagram shows a multi-writer configuration in the vSphere Web Client.



There are many cluster filesystem software’s available which can take advantage of this multi-writer option. Here are the VMware KB articles and resources that provide more details on some of the popular cluster solutions that use the multi-writer option:


Oracle Real Application Cluster (RAC)

Using Oracle RAC on a vSphere 6.x vSAN Datastore (KB 2121181)

Oracle RAC on vSAN (Reference Architecture).

Oracle RAC on VMware Cloud on AWS (VMware Blog)


Redhat Clustering Suite

Using Red Hat Clustering Suite on a vSphere 6.x vSAN Datastore (KB 2151774)


Veritas InfoScale Enterprise

vSAN datastore support for InfoScale Enterprise (Veritas Technote)

Veritas InfoScale Enterprise support for VMware ESXi guests (KB 000051476).



Some business-critical applications require shared access to a virtual disk. VMFS and vSAN datastores support the use of the multi-writer option to provide multiple virtual machines shared access to a virtual disk. vSAN offers support for common and niche use cases required for smooth journey to HCI while providing the benefits of efficient, high performance and cost effective HCI platform for business-critical applications.


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