Differences Between VMFS 5 vs VMFS 6 and How to Migrate from VMFS 5 to 6

VMware's Virtual Machine File System (VMFS) is the go-to format for most system admins and IT professionals for storing their VM data. This is because the VMFS format is much more flexible and supports many applications.

Basically, VMFS is the standard file system format for vSphere and other VMware virtualization platforms. VMware releases new versions of its VMFS storage format from time to time – the newest versions being VMFS 5 and VMFS 6.

As everyone would guess, the newer version, VMFS 6, definitely comes with improved features and increased support than the VMFS 5. But then, there are applications where VMFS 5 will be the better choice to stick with. This article compares the VMFS 5 and VMFS6 in crisp detail.

VMFS 5 Overview

Launched with vSphere 5.0, VMFS 5 extended storage limits from 50TB to 64TB, with file size limits increased up to 62 TB. However, older vSphere versions (prior to 5.5) can only handle VMDKs smaller than 2TB, with the 62TB limit applicable to versions after 5.5. Despite the release of VMFS 6, many IT admins continue to use VMFS 5 due to its MBR partitioning support, compatibility with vSphere 6.0, and other newer versions. Its major limitation is the restricted space allocation from guest OSes.

Table Comparison

To clearly understand the difference between VMFS 5 and VMFS 6, here’s a chart table. Actually, both versions have more similarities than differences.

• 512n: A traditional hard disk drive (HDD) that supports 512-byte-size physical sectors.
• 512e: Newer format. Connotes 4k sectors emulated as 512n – “native.” 
• 4Kn: This refers to a local 4K-native disk drive that doesn’t emulate 512-byte sectors; hence, both physical and logical sectors of the drive will remain 4096 bytes. If you’re running a RAID with 4Kn drives, the drives must support native 4K sectors. Starting with the v6.7, VMware ESXi and VMFS support 4Kn disk drives. 
• Master Boot Record (MBR): A disk partition format that stores not larger than 2.2TB data and four primary partitions.
• GUID Partition Table (GPT): A newer disk partition format cable for storing larger files >2TB with support for more than four primary partitions.
• Raw Device Mapping (RDM): Allows you to connect physical drives or a LUN to a VM directly.

LUN (Logical Unit Number): Used to indicate logical units on SCSI-based disks using an addressing scheme: Bus 🡺 Address (ID) 🡺 LUN.

How to Upgrade VMFS 5 to 6 in the Command Line

If you have a vCenter Server inventory of registered VMs running from a VMFS 5 datastore (DS-A) and the datastore (DS-A) also has orphaned data not registered in the vCenter inventory, then try this method to upgrade to VMFS 6. This method requires knowledge of vSphere PowerCLI.

Pre-Requisites:

• Recheck the version(s) of all ESX hosts and vCenter Server(s)
• You should move all ESXi hosts and vCenter Server to vSphere 6.5 before proceeding with the steps below. 
• There should be an alternative free datastore (DS-B), which should be of the same space capacity or higher than the one you want to upgrade. This alternative datastore (DS-B) should be running on VMFS 6.

Steps: 

• Launch the command-line utility and run this command: Get-Datastore | Select Name, FileSystemVersion
• Followed by this command: esxcli storage filesystem list
• Check for all datastores and their devices identifiers (IDs): esxcfg-scsidevs -m
• Identify a free VMFS 6 disk where you will move files– use df -h command to see disk usage information. 
• Evacuate DS-A (migrate the data to the alternative DS-B) using this command: cp -R /vmfs/volumes/DS-A/ISO /vmfs/volumes/DS0-B. 
• Note: To copy thin provisioned disks, use: vmkfstools -i -d thin
• If there errors during the migration, note it down and re-trigger the migration for the affected VMs.
• List out all the orphaned files that are not on your vCenter Server and move them to the DS-B one at a time. 
• Once you have emptied DS-A, unmount it from all ESX hosts, then proceed to delete it: vmkfstools -C vmfs6 /vmfs/devices/disks/
• Now, create a new datastore to run VMFS 6 filesystem and rename the new datastore using the same LUN as the deleted one – DS-A. 
• Run a storage rescan command for all ESX hosts and wait until the process completes. 
• Move back all your virtual machines from DS-B to DS-A by running the storage vMotion operation. Again, move only one VM at a time and note down error logs (if any). 
• Move back the orphaned data files, too.

Note: This method does not support Storage DRS and SDC reliably because datastore maintenance operation evacuates only datastores with known VM objects.

What More?

The standard VMFS Recovery tool from VMware works too, but has limited features – DiskInternals VMFS Recovery comes with many features and tools, while also including RAID Recovery features. You can run VMFS Recovery on any Windows PC; thanks to the intuitive interface, anyone can easily understand and use the tool. 

To be on the safe side when migrating from one VMF version to another, it is important to back up your data. Even so, VMware vSphere Data Protection comes with a number of handy features to protect your VM data against mission-critical applications using agents. This native tool seamlessly integrates with VMware’s products. 

Finally, upgrading from VMFS 5 to VMFS 6 is best done using the vSphere Client, which is GUI-based. It is faster, more intuitive, and easier to use. The command-line method is only recommended when you have orphaned files that need to be moved separately.

FAQ