[Solved] Failed to Increase VMFS Capacity in VMware ESXi

VMFS datastore is commonly used in VMware ESXi to store virtual machine files. Did you have the problem of insufficient space in VMFS datastore? So in this article, you can find the solutions to increase VMFS capacity.


By Crystal / Updated on December 7, 2022

Share this: instagram reddit

Case: Failed to expand VMFS datastore

I am trying to increase the storage space in ESXi host. I have added a 1TB HDD to the array successfully and the datastore shows the size correctly 2.73TB. Unfortunately, the datastore is on the same array as the ESXi host, so expanding from the 6.5 GUI does not work. It is throwing an error: Failed to expand VMFS datastore datastore1 - Cannot change the host configuration. Any ideas?


Failed to expand VMFS datastore in VMware ESXi

VMFS Datastores in VMware ESXi can be expanded in capacity by adding a new extent on a different storage device, or by increasing the size of the existing storage device and then growing the existing datastore extent to fill that available adjacent capacity. But in the process, you may find the error note: Fail to expand VMFS datastore - Cannot change the host configuration.

failed expand vmfs datastore

The reason for this error is that the datastore resides on the same volume as ESXi installation, so the only way to expand VMFS datastore is to use the command line. But in this case, the embedded host client still allows you to go through the expand storage wizard, which is a bug.

Tip: It is also possible that the ESXi Hypervisor (Free) Web Client is not supported by Firefox and you can try Chrome, as reported by some users.

So in the following part, I will explain how to expand VMFS datastore step by step, please refer to whether you follow the correct steps and find out why you cannot extend VMFS database in vSphere Web Client, or directly refer to the second part to use command line to increase VMFS capacity.

How to expand VMFS datastore via vSphere Web Client

If you want to utilize the free space of datastore 1 properly, you can migrate files to another datastore with additional space or use vSphere Web Client to expand VMFS datastore.

1. Access to Storage in vSphere Web Client interface and click the datastore which needs to increase the capacity, then select Increase capacity.

increase vmfs capacity

2. In the opened window, select Expanding an existing VMFS datastore extent.

expand an existing vmfs

3. Select device, you can notice the capacity and free space of the datastore.

select device

4. Adjust the slider to allocate the free space to the VMFS partition. Then review the information and click Finish to close the window.

Tip: The maximum size of a VMFS datastore for VMFS6 is 64TB. Storage may consist of one LUN or up to 32 extents with a total size up to 64TB.

allocate free space

After allocating extra space to increase the VMFS data capacity, if an error note pops up showing Fail to expand VMFS datastore - Cannot change the host configuration, it failed to increase VMFS capacity through vSphere Web Client. So please try the command line to expand VMFS datastore.

Extend VMFS datastore using Command Line

1. Remember the disk and partition information first before expanding the VMFS datastore. Then enable SSH and connect to your ESXi host.

extent infromation

2. Run the following command to check the partition on the disk via SSH.

partedUtil getptbl "/vmfs/devices/disks/DeviceName"

extend vmfs datastore command line

Locate and check the 8th partition, it is what we will expand.

3. Enter partedUtil fixGpt "/vmfs/devices/disks/DeviceName" to confirm if there are any problems with the partition we will be processing and fix them timely. Press Y.

confirm vmfs datastore

Write down the number of starting sector of the VMFS partition is 268437504.

4. Find the end sector by entering this command.

partedUtil getUsableSectors "/vmfs/devices/disks/DeviceName"

The VMFS datastore ends at the sector 524287966.

vmfs end sector

5. From the previous commands, you can easily expand the partition

partedUtil resize "/vmfs/devices/disks/DeviceName" PartitionNumber NewStartSector NewEndSector

expand vmfs command line

It’s successful to extend the partition.

6. Next you need to grow the VMFS file system.

vmkfstools --growfs "/vmfs/devices/disks/DeviceName:PartitionNumber" "/vmfs/devices/disks/DeviceName:PartitionNumber"

grow vmfs file system

Now you can log into you vSphere Web Client to check the expanded capacity of VMFS datastore.

Although these solutions are able to solve your problem, I still strongly recommend that you should back up VMware datastore to avoid any errors in the process that could threaten your data security or cause financial losses.

Protect VMware VMs in datastore with reliable backup tool

For enterprise, data security is crucial for business development. Here, I’d like to use the professional VMware backup solution AOMEI Cyber Backup to schedule a VMware backup task. It is easy to use since all steps are based on clicks, and it offers an error-free and affordable backup & recovery plan for VMware virtual machines. It supports both paid and free versions of VMware ESXi 6.0-7.0.

You can download the 30-day free trial to experience its features:

Download Free TrialVMware ESXi & Hyper-V
Secure Download

*You can choose to install this VM backup software on either Windows or Linux system.

1. Download AOMEI Cyber Backup and add vCenter or Standalone ESXi host as the source device.

add VMware ESXi

2. Create Backup Task: specify the task name and select the virtual machines you want to backup. You can batch backup large numbers of VMs managed by vCenter Server, or multiple VMs on a standalone ESXi host.

In Target, select local or network path to store the virtual machine data.

VMware ESXi backup target

In Schedule, select multiple backup methods as full / incremental / differential backup and set up a time to run it automatically.

schedule VMware ESXi backup

In Backup Cleanup, specify retention policy to delete old backup files automatically.

delete backup files

3. Restore: You can restore the whole VM and virtual environment within a few clicks. If the datastore has been damaged, you can choose Restore to new location and easily recover the VMware VM to a new datastore or even host. It doesn’t require reinstalling and configuring virtual machine.

restore VMware ESXi


This article introduces the solutions of failing to expand VMFS datastore. If your datastore is on the same array as the ESXi host, you can only use  command line that is also fast and efficient to increase VMFS capacity.

In VMware datastore, snapshots size is easy to occupy the storage, do not forget to delete the unwanted snapshots timely.

Crystal · Editor
Crystal is an editor from AOMEI Technology. She mainly writes articles about virtual machine. She is a positive young lady likes to share articles with peolpe. Off work she loves travelling and cooking which is wonderful for life.