What is VMware VMFS 5?

VMFS5: 

• VMware proprietary file system that is virtualization aware and optimized for virtualization. 
• Supports concurrent access to shared storage. 
• Can be expanded dynamically. 
• Uses a 1 MB regular block size, for storing large virtual disk files. 
• Uses sub-block addressing, storing small files: the sub-block size is 8 KB.

Note: 

1. If file size is less than 1 KB, file is stored in metadata space. No blocks/sub-blocks are used.
2. If file size is more than 1 KB but less than 8 KB, sub-block is used to store the file.
3. If file size is more than 8 KB, regular block is used.

• Provides on-disk, block-level locking.

There 2 methods used under on-disk, block level locking as below.

• SCSI Reservation
• ATS (Atomic Test and Set) - Default method if your storage has VAAI plugin support.