Virtual Data Storage

Virtual data storage technology provides a better way to manage storage resources for a virtual infrastructure, offering the ability to:

Increase storage resource utilization and flexibility.
Reduce management overhead
Increase application uptime.
Manage the diversity of the existing storage infrastructure.

Storage virtualization increases resource utilization by providing multiple virtual machines with shared access to a consolidated pool of clustered storage devices. It provides the foundation for distributed infrastructure services such as live migration of virtual machines and virtual disk files, as well as live storage migration, distributed resource scheduling, consolidated backup and automated disaster recovery.

As an automated file system, virtual data stores all the files that make up the virtual machine in a single directory. Optimized to support large files and also performing many small concurrent writes. With automated handling virtual machine files, the virtual data store provides encapsulation of the entire virtual machine so that it can easily become part of a disaster recovery solution.

As a logical volume manager, the virtual data store enables an interface to storage resources so that several types of storage (SAN, iSCSI and NAS) can be presented as datastores on which virtual machines can reside. Enabling dynamic growth of those datastores through aggregation of storage resources and dynamic expansion of disk space. As such, a virtual data environment provides the ability to increase a shared storage resource pool with no downtime. And it also provides a means for mounting a point in time copy of a datastore.

Conventional file systems allow only one server to have read-write access to the same file at a given time. By contrast, in a virtual data environment shared storage allows multiple instances of servers have concurrent read and write access to the same shared storage resources.
The virtual data store utilizes distributed journaling of its file system meta data changes to allow fast and resilient recovery across these multi-server resource pools.

The virtual data store can reduce or eliminate planned downtime by enabling live migration of virtual datastores across heterogeneous arrays with no disruption in service.

(text derived from http://www.vmware.com/technical-resources/virtual-storage/)