Tuesday, June 5, 2012

Considerations – Upgrade or Create New (VMFS-5)

While a VMFS-3 which is upgraded to VMFS-5 provides you with most of the capabilities as a newly created VMFS-5, there are some differences. Both upgraded and newly created VMFS-5 support single-extent volumes up to 64TB and both support VMDK sizes of ~2TB, no matter what the VMFS file-block size is. However additional differences, although minor, should be considered when making a decision whether to upgrade to VMFS-5 or create new VMFS-5 volumes.

No Uniform Block Size

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. This can lead to stranded/unused disk space when there are lots of small files on the datastore.

No New Sub-Block Size

VMFS-5 upgraded from VMFS-3 continues to use 64KB sub-blocks and not the new 8KB sub-blocks. This can also lead to stranded/unused disk space. The upgraded VMFS-5 also continues to use the original number of sub-blocks from the VMFS-3.

No Increase to the Maximum Number of Files per Datastore

VMFS-5 upgraded from VMFS-3 continues to have a file limit of 30,720 rather than new file limit of > 100,000 for newly created VMFS-5. This has an impact on the scalability of the file system.

Uses MBR

VMFS-5 upgraded from VMFS-3 continues to use MBR (Master Boot Record) partition type; when the VMFS-5 volume has grown beyond 2TB, it automatically and seamlessly switches from MBR to GPT (GUID Partition Table) with no impact on the running virtual machines.

Starts on Sector 128

VMFS-5 upgraded from VMFS-3 continues to have its partition starting on sector 128. Newly created VMFS-5 partitions will have their partition starting at sector 2048.

For more details you can see the link below:-

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