VMFS-3 >> VMFS-5

The first new feature I am going to focus on in vSphere 5 is VMFS-5. As you know within VI3.x & vSphere 4.x VMFS-3 was used. So whats changed?  VMFS-5 offers the following enhancements:

• A unified 1MB file block size
• 64TB datastores without increasing extents. This is a massive increase on the previous 2TB single extent datastore limit using VMFS-3
• Smaller Sub Block now uses 8KB instead of 64KB. Reducing the amount of disk space being consumed by small files
• VMFS-5 uses the file descriptor location in the metadata for storage rather than files blocks. When files grow above 1KB these files will then start to use the new 8KB sub blocks, resulting again in reduced amount of disk being consumed by very small files.
• Support for more than 100,00 files in a datastore, that's three times the number of files supported within a VMFS-3 datastore  
• vStorage API for Array Integration (VAAI) hardware acceleration locking used more extensively improving file locking performance over VMFS-3

Wow, so how do you migrate from VMFS-3 to VMFS-5? Those that performed VMFS-2 to VMFS-3 upgrades will remember remember the complex scripts that required running to perform the upgrade. However I am happy to confirm the upgrade from VMFS-3 to VMFS-3 is non disruptive, easy to perform, takes only a matter of minutes and can be simply completed via the vSphere 5 Client (see screenshots below)

Right, now you know the benefits of VMFS-5 compared to VMFS-3 and the fact the upgrade process is non-disruptive, simple and takes minutes. However here comes the curveball ...  The upgrade from VMFS-3 to VMFS-5 only provides you with the following new features:

• 64TB datastore limit
• 64TB physical passthu RDM limit
• The max size of a non-passthru (virtual RDM) on VMFS-5 is still 2TB -512 bytes
• The max size of a file (i.e. .VMDK) on VMFS-5 is still 2TB -512 bytes
• It is also worth noting that VMFS-3 to VMFS-5 is a one way road. After you convert to VMFS-5 you CANNOT revert to VMFS-3 without creating a new VMFS-3 datastore

So what happened to the other new sparkly features in VMFS-5? The following features are only available on newly create VMFS-5 datastores:

• Unified 1MB Block Size
• 8KB Sub Blocks
• Increased file limit of more than 100,000 files in a datastore
• Extensive use of VAAI hardware acceleration locking

As you can see upgrading to VMFS-5 from VMFS-3 means you don't get all of the goodness included in VMFS-5. Based on this information it appears the best approach is to create a new set of VMFS-5 datastores (if you have the additional storage available or are considering purchasing new storage for your vSphere 5 datastores) and Storage vMotion all of your virtual machines from your VMFS-3 datastores to your new VMFS-5 datastores. Further details regarding VMFS-5 an be found here