By now, regular readers of this blog will be aware that VMFS-5 supports a single extent volume size of 64TB. In an earlier post, I mentioned that newly created VMFS-5 partitions use a GUID Partition Format, GPT. This partition format allows for the creation of large partition sizes to cater for the new single extent 64TB VMFS-5 volume.
But what about VMFS-3 volumes, which were created with the MBR (Master Boot Record) format, and are subsequently upgraded to VMFS-5? MBR has a maximum partition size of ~ 2TB, so does this mean that VMFS-3 filesystems upgraded to VMFS-5 are still limited by this partition format? The answer is no. The partition format will change automatically & seamlessly from MBR to GPT when the size of the upgrade VMFS-5 volume is grown above the 2TB threshold. This change can also occur when the VMFS-5 has VMs powered on and running. The change-over to the new partition type is non-disruptive. I've alluded to this in previous posts. In this post I wanted to show you a little more detail.
Let's have a closer look: In this example, I have a LUN presented to my ESX. The LUN is 3TB in size as is presented from a NetApp FAS 3170A over FCoE. I will now create a 2TB VMFS-3 volume on it, with 1TB of unused space remaining on the LUN. Note that the partition table is MBR.
Note that because the partition format is MBR, we can continue to use fdisk in the CLI to examine this disk:
The next steps are to upgrade this volume to VMFS-5, and then grow the volume above the 2TB threshold. Once these steps are initiated, we will observe the automatic switching of the partition format from MBR to GPT.
Here is the view of this volume before the upgrade:
Just above the Datastore Details, on the right hand side, there is the option to Upgrade to VMFS-5. This is another cool feature and allows you to do an online non-disruptive upgrade of a VMFS-3 volume to VMFS-5. Click this option, and the following message is displayed:
Once the upgrade has completed, we can now see the properties of the datastore reflect that it is now a VMFS-5 volume:
But the point is that this disk, although it now has a VMFS-5 volume on it, continues to use MBR. It is only when this volume is grown above 2TB that the partition format changes to GPT. Let's do that next.
The LUN that we presented from the NetApp is 3TB in size, although we only used 2TB when we initially built the VMFS-3 volume. We will use that 1TB of free space to grow the volume to 3TB:
Once the online grow operation has been completed, the VMFS-5 volume (upgraded from VMFS-3) should now show a new size of 3TB:
Let's now look at the partition format using the fdisk command at the CLI:
Ah, this is interesting. fdisk no longer works on this disk. The partition format is no longer MBR, but as the fdisk command states, it has found a valid GPT. VMware prevents fdisk from being used on GPT to prevent customers inadvertently damaging the GPT partition table. As the message states, we should now be using partedUtil to query GPT disks. Let's do that:
Now our 3TB VMFS-5 volume is using GPT, and have seamlessly switched to this new format. The only thing we did was grow the volume above 2TB. Everything was taken care of automatically. And the point is that this can be done online and non-disruptively, even with VMs running on the datastore.
To learn more about VMFS-5 features, take a look at this earlier posting from around the time of the vSphere 5.0 launch.
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Nick B
I’m assuming the file block size will remain the same as the VMFS-3 datastore, even on the format change?
i.e. 8mb FBS on vmfs-3 = 8mb FBS on vmfs-5
Is there anyway to change? SvMotion from vmfs-3 datastore to newly created vmfs-5 datastore with 1mb FBS specified?
Nick B
Never mind. The link to your previous article explained it perfectly.
http://blogs.vmware.com/vsphere/2011/07/new-vsphere-50-storage-features-part-1-vmfs-5.html
Thanks!
Satya Dev
Great Stuff. Thanks a lot for the article. You made it look very easy 🙂
Troy MacPherson
VMWare 5.0 does not support larger than 2TB on a direct attached SCSI… I have 10TB of available storage but still can only use 2TB at a time… I cannot believe we were lead to believe upgrading to v5.0 would fix this…
Chogan
Troy,
I’m not sure what you mean by ‘fix’, but vSphere 5.0 does most definitely supports larger than 2TB VMFS-5 on direct attached storage. I suspect the issue you are experiencing is RAID controller/driver specific. Please see the 5.0 configuration maximums guide (http://www.vmware.com/pdf/vsphere5/r50/vsphere-50-configuration-maximums.pdf) page 4, footnote 7. This is in relation to the maximum size of a VMFS-5 volume. The footnote states – ‘The actual maximum will depend on the RAID controller or adapter driver that is being used. Contact
your vendor to find the maximums.’
Humphrey Widjaja
when we upgrade vmfs3 to vmfs5, does it mean the first 2tb is mbr and next to 64tb is gpt? We’ll get two partitions.
Chogan
Hello Humphrey,
No, you will not get 2 partitions. Whilst the volume remains below 2TB in size, it will use the MBR format. When the volume grows above 2TB, it will automatically switch the partition format to GPT.
Humphrey Widjaja
i was told by vmware consultant that there will be 2 partitions. thanks so much for answering my question.
Tony Coaxum
I have upgraded my datastores. The question is are the VMs that were running on it before I upgraded, now using vfms5, or do I need to migrate them off and then back onto the datastore?
Cormac
Nope – you don’t need to do anything else.
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Is there a way to convert MBR vmdk to GPT inside the OS (Windows Server 2012 R2)? I can’t use any third party conversion tool and am trying to avoid doing a backup and restore to newly GPT partitioned disk as SQL resides on it.