VMFS-5 Enhancements

•  Unified 1MB File Block Size. Previous versions of VMFS used 1,2,4 or 8MB file blocks. These larger blocks were needed to create large files (>256GB). Very large files can now be created on VMFS-5 using 1MB file blocks.
•  Large Single Extent Volumes. In previous versions of VMFS, the largest single extent (LUNs) was 2TB. With VMFS-5, this limit has been increased to ~ 60TB.
•  Smaller Sub-Block. VMFS-5 introduces a smaller sub-block. This is now 8KB rather than the 64KB we had in previous versions. Now small files < 8KB (but > 1KB) in size will only consume 8KB rather than 64KB. This will reduce the amount of disk space being stranded by small files.
• Small File Support. VMFS-5 introduces support for very small files. For files less than or equal to 1KB, VMFS-5 uses the file descriptor location in the metadata for storage rather than file blocks. When they grow above 1KB, these files will then start to use the new 8KB sub blocks. This reduce the amount of disk space being stranded by very small files.
•  Increased File Count. VMFS-5 introduces support for greater than 100,000 files, a three-fold increase on the number of files supported on VMFS-3, which was ~ 30,000.
•  ATS Enhancement. This Hardware Acceleration primitive, Atomic Test & Set (ATS), is now used throughout VMFS-5 for file locking. ATS is part of the VAAI (vSphere Storage APIs for Array Integration). This enhancement improves the file locking performance over previous versions of VMFS.

Differences between newly created and upgraded VMFS-5 datastores:

•     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.

•     VMFS-5 upgraded from VMFS-3 continues to use 64KB sub-blocks and not new 8K sub-blocks.

•     VMFS-5 upgraded from VMFS-3 continues to have a file limit of 30720 rather than new file limit of > 100000 for newly created VMFS-5.

•     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 & seamlessly switches from MBR to GPT (GUID Partition Table) with no impact to the running VMs.

•     VMFS-5 upgraded from VMFS-3 continue to have its partition starting on sector 128; newly created VMFS5 partitions will have their partition starting at sector 2048.

RDM – Raw Device Mappings

•     There is now support for passthru RDMs (Physical Mode)  to be ~ 60TB in size.

•     Non-passthru RDMs (Virtual Mode) are still limited to 2TB – 512 bytes.

•     Both upgraded VMFS-5 & newly created VMFS-5 support the larger passthru RDM (Physical Mode)

Some More Information.

•     The maximum size of a VMDK on VMFS-5 is still 2TB -512 bytes.

•     The maximum size of a non-passthru (virtual) RDM on VMFS-5 is still 2TB -512 bytes.

•     The maximum number of LUNs that are supported on an ESXi 5.0 host is still 256.

Thanks to VMware, Information is from the white paper provided by VMware.