By New vSphere 6 .5 has been release with New File system after VMFS 5 released in 2011. Good news is that VMFS6 supports 512 Devices and 2048 Paths. In previous versions the limit was 256 devices and 1024 paths and some customers were hitting this limit in their cluster. Especially when RDMs are used or people have a limited number of VMs per datastore, or maybe 8 paths to each device are used it becomes easy to hit those limits. Hopefully with 6.5 that will not happen anytime soon.
Automatic Space Reclamation is the next feature that many of customers/administrators have been waiting for. basically this is based on VAAI Unmap which has been around for a while and allows you to unmap previously used blocks. using Unmap storage capacity is reclaimed and released to the array so that when needed other volumes can use those blocks. Previously we need to run Unmap command to reclaim the blocks, now this has been integrated in the UI and can be turned on or off from GUI.
SESparse will be the snapshot format supported on VMFS6, vSphere will not be supporting VMFSparse snapshot format in VMFS6, it will continue to be supported on VMFS5. Both VMFS 6 and VMFS 5 can co-exist but there is no straight forward upgrade from VMFS5 to VMFS6. After you upgrade your ESXi hosts to version 6.5, you can continue using any existing VMFS5 datastores. To take advantage of VMFS6 features, create a VMFS6 datastore and migrate virtual machines from the VMFS5 datastore to VMFS6 datastore. You cannot upgrade the VMFS5 datastore to VMFS6. right now SE Sparse is used primarily for View and for LUNs larger than 2TB. with VMFS 6 the default will be SE Sparse.
Comparison is as below:
| Features and Functionalities | VMFS5 | VMFS6 |
| Access for ESXi 6.5 hosts | Yes | Yes |
| Access for ESXi hosts version 6.0 and earlier | Yes | No |
| Datastores per Host | 1024 | 1024 |
| 512n storage devices | Yes (default) | Yes |
| 512e storage devices | Yes. Not supported on local 512e devices. | Yes (default) |
| Automatic space reclamation | No | Yes |
| Manual space reclamation through the esxcli command. | Yes | Yes |
| Space reclamation form guest OS | Limited | Yes |
| GPT storage device partitioning | Yes | Yes |
| MBR storage device partitioning | Yes
For a VMFS5 data store that has been previously upgraded from VMFS3. |
No |
| Storage devices greater than 2 TB for each VMFS extent | Yes | Yes |
| Support for virtual machines with large capacity virtual disks, or disks greater than 2 TB | Yes | Yes |
| Support of small files of 1 KB | Yes | Yes |
| Default use of ATS-only locking mechanisms on storage devices that support ATS. | Yes | Yes |
| Block size | Standard 1 MB | Standard 1 MB |
| Default snapshots | VMFSsparse for virtual disks smaller than 2 TB.
SEsparse for virtual disks larger than 2 TB. |
SEsparse |
| Virtual disk emulation type | 512n | 512n |
| vMotion | Yes | Yes |
| Storage vMotion across different datastore types | Yes | Yes |
| High Availability and Fault Tolerance | Yes | Yes |
| DRS and Storage DRS | Yes | Yes |
| RDM | Yes | Yes |
