VMFS - VMware Virtual Machine File System

Block Size details 

Extents :

Extents are nothing but the physical partitions we can call them as LUN. We  can have maximum 32 extents for a data store . 

Extents can  be filled irrespective whether the old extent is full or empty . 

• For VMFS 3 , Max extent size is 2 TB . This is due to the MBR partition . So , Maximum datastore capacity is 64 TB 
• For VMFS 5 , max extent size is 64 TB . The data store capacity can grow as much as 64 TB. It can be a single extent or multiple extents
  

Difference Between the VMFS 3 and VMFS 5 

Differences between upgraded and newly created VMFS-5 datastores:

1. VMFS-5 upgraded from VMFS-3 continues to use the previous file block size which may be larger than the unified 1MB file block size. Copy operations between datastores with different block sizes won’t be able to leverage VAAI.  This is the primary reason I would recommend the creation of new VMFS-5 datastores and migrating virtual machines to new VMFS-5 datastores rather than performing in place upgrades of VMFS-3 datastores. (NOTE : Block Size – 1 , 2 ,4 8 MB )
2.  VMFS-5 upgraded from VMFS-3 continues to use 64KB sub-blocks and not new 8K sub-blocks.
3. VMFS-5 upgraded from VMFS-3 continues to have a file limit of 30,720 rather than the new file limit of > 100,000 for newly created VMFS-5.
4. VMFS-5 upgraded from VMFS-3 continues to use MBR (Master Boot Record) partition type; when the VMFS-5 volume is grown above 2TB, it automatically switches from MBR to GPT (GUID Partition Table) without impact to the running VMs.
5.  VMFS-5 upgraded from VMFS-3 will continue to have a partition starting on sector 128; newly created VMFS-5 partitions start at sector 2,048.