Extending VM Disk to be larger than 2 TB ?

Senior IT System Engineer
Senior IT System Engineer used Ask the Experts™
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Hi All,

I've got one VMware VM that is running Windows Server 2008 R2 with the size of 1.9 TB the VMDK
it is running out of disk space at the moment.

So if I extend it to be 2.7 TB, would it be any problem later on with vSphere 5.5 or Veeam backup or maybe Windows itself ?
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Rajul RajInformation Security Officer
Commented:
Hi,

There is no issues if you extend the size of a Virtual Disk, But be caution for the below points.

1. The size of the disk partition does not increase as observed inside the guest operating system.
2. You must back up your virtual machine before increasing the size of virtual disks.
3. All the snapshots should be removed.
4. The virtual machine is powered off.
A Windows legacy boot disk can't be larger than 2TB. Also any disk space after that 2 TB border is lost.
An additional (non-boot) disk (separate VMDK) could be larger.

Author

Commented:
Is there any maximum limit that I need to be aware of ?

Author

Commented:
Somehow this old VM was built by just one 1.9 TB VMDK and then the partition is MBR NTFS:

C:\ 100 GB
D:\ 1800 GB

The D drive is now running out of disk space.
Can I still expand it to more than 2 TB for the D:\ drive ?
https://support.microsoft.com/en-us/help/2581408/windows-support-for-hard-disks-that-are-larger-than-2-tb
explains the 2TB limit . I assume the system hasn't been set up with GPT.

You can extend it to > 2TB under VMWare but I you won't be able to extend the disk beyond 2TB in Windows.
Rajul RajInformation Security Officer

Commented:
Even though 5.5 supports max VMDK size 62TB, VI client will continue to show it as 2TB as all new features from 5.5 are supported in Web client. If you check the same from web client, it will definitely show 62TB VMDK as max size. If you want to create VMDK size more than 2TB, you will have to use web client. All features upto 5.1 are fully supported on VI client.
I'd say you can add another 100 GB, thats it.
You can create a bigger VMDK, but Windows won't be able to use it.

You could create a new VMDK, attach it, copy all data from D:\ to the new VMDK and swap drive letters. Will take a while, use double space and I'm not sure if you can shrink the first VMDK after the migration.
VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017
Commented:
Windows disks larger than 2TB need to be GPT.

So what partition type is currently in use MBR (default) or GPT.

If it's MBR, you will need to convert MBR to GPT, or start again with a new disk of GPT and the correct size and then robocopy.
There seem to be tools available to convert an MBR disk to a GPT disk.
http://www.thewindowsclub.com/convert-mbr-to-gpt-disk

I would definitely not try that on an important machine.

Author

Commented:
Thank you !

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