VMFS5 provides many improvements in scalability and performance over the previous version.

VMFS5 has the following improvements:

Greater than 2TB storage devices for each VMFS extent.

Increased resource limits such as file descriptors.

Standard 1MB file system block size with support of 2TB virtual disks.

Greater than 2TB disk size for RDMs in physical compatibility mode.

Support of small files of 1KB.

With ESXi 5.1, any file located on a VMFS5 datastore, new or upgraded from VMFS3, can be opened in a shared mode by a maximum of 32 hosts. VMFS3 continues to support 8 hosts or fewer for file sharing. This affects VMware products that use linked clones, such as View Manager.

Scalability improvements on storage devices that support hardware acceleration. For information, see Storage Hardware Acceleration.

Default use of hardware assisted locking, also called atomic test and set (ATS) locking, on storage devices that support hardware acceleration. For information about how to turn off ATS locking, see Turn off ATS Locking.

Ability to reclaim physical storage space on thin provisioned storage devices. For information, see Array Thin Provisioning and VMFS Datastores.

Online upgrade process that upgrades existing datastores without disrupting hosts or virtual machines that are currently running. For information, see Upgrading VMFS Datastores.

For information about block size limitations of a VMFS datastore, see the VMware knowledge base article at http://kb.vmware.com/kb/1003565.