A comparison of VMFS5 & VMFS6 in vSphere 6.5

vSphere 6.5 has introduced a new VMFS version 6 and there are a few changes in it compared to VMFS version 5 that you should be aware of. You have to love VMware’s crazy out of sync versioning across their product lines, now naturally you would think vSphere 6.0 would have VMFS6 in it but VMware kept it at VMFS5 with an incremental version and VMFS6 is new with vSphere 6.5. The table below highlights the difference between the two that you should be aware of but I also wanted to make you aware of some additional info you should know when upgrading to vSphere 6.5 or operating in a mixed vSphere version environment.

The first is once again you can’t upgrade in place existing VMFS5 volumes to VMFS6. That royally sucks and you have to plan migrations by creating new VMFS6 datastores, migrating VMs to them with Storage vMotion and then deleting the VMFS5 datastores when you are done to get back your disk space. Depending on your environment and how much space you have available on your array this can be a long and painful migration. [BEGIN VVols Plug] With VVols you don’t have to deal with any of that BS as you aren’t using VMFS and don’t have to constantly upgrade a file system [END VVols Plug]

Now you might think, screw that, a file system is just a file system and I’ll stick with VMFS5, but you miss out on the automatic space reclamation that is finally back in vSphere 6.5. Be aware that the new 512e drive support in vSphere 6.5 is supported on either VMFS6 or VMFS5 as long as the host is running ESXi 6.5. Beyond that there isn’t too much difference between the two, they also both now support 512 LUNs/VMFS datastores per host as well (note vSphere 6.5 storage doc incorrectly states 1024). So you may end up sticking with VMFS5 but I think the automatic reclamation does make for a compelling use case to upgrade to VMFS6.

So it’s up to you to decide, if you want to learn more be sure and look through the vSphere 6.5 storage documentation, and if you are fed up with VMFS upgrades and want something way cooler give VVols a serious look.

Feature & FunctionalityVMFS6VMFS5
Can vSphere 6.5 host access?YesYes
Can vSphere 6.0 and earlier hosts access?NoYes
VMFS Datastores per Host512*512*
512n storage device supportYesYes
512e storage device supportYesYes (Not on local 512e devices)
Automatic space reclamation (UNMAP)YesNo
Manual space reclamation (esxcli)YesYes
Space reclamation within guest OSYesLimited
GPT storage device partitioningYesYes
MBR storage device partitioningNoYes
Block size1MB1MB
Default snapshot typeSEsparseVMFSsparse (virtual disks < 2 TB SEsparse (virtual disks > 2 TB)
Virtual disk emulation type512n512n
Support of small files of 1 KBYesYes

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  1. I was looking at VMFS5 vs VMFS6 as we want the SCSI unmap capability. In this article, https://kb.vmware.com/s/article/2147824, it dealt with those of us that already started a project with VMFS5 and have to upgrade to VMFS6. I found article very helpful with its upfront warning to be sure to COMPLETE ALL VCENTER AND ESXI HOSTS UPGRADE TO AT LEAST 6.5—BEFORE ATTEMPTING ANY VMFS5 to VMFS6 UPGRADE OF THE DATASTORE:

    To upgrade:

    Perform version check for the vCenter Server and all ESX hosts.

    Note: All ESXi hosts and vCenter Server must be of vSphere 6.5. Do not proceed if any one of ESXi hosts is not vSphere 6.5. Proceeding further means business continuity loss and the new datastore is not visible in old ESX hosts.

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