VMFS Recovery™Recover data from damaged or formatted VMFS disks or VMDK files
VMFS Recovery™
Recover data from damaged or formatted VMFS disks or VMDK files

What is Space Reclamation

Here you will find out:

  • what is VMware space reclamation
  • how can you use it
  • how DiskInternals can help you

Are you ready? Let's read!

VMware space reclamation

VMware space reclamation


Both VMFS 6 and VMFS 5 support the space reclamation function.

So what is it, and why is it needed?

As soon as any information is deleted from storage, the blocks are also freed.

But arrays do not know about this and so these blocks remain marked as “taken”.

The space reclamation function helps the array to understand that it is time to free the blocks, since there are no data any more.

In order for all this to happen as simply and quickly as possible, VMFS uses the UNMAP command.

Moreover, in different versions of VMFS, there may be some differences in the execution of this command; for example, new versions of VMFS 6 carry out space reclamation automatically, but in VMFS 5 you will have to set tasks manually.

Of course, in this case, experience is needed.

So why does that is important?

Because there are common thin provision use, which means that is essential to free up space from deleted data and bring it back to the pool of available storage.

About dead space

Dead space certainly accumulates during VM operation, and if it is not freed up, then system interruptions can occur.

Basically, there are two places where this unused space comes from:

  • The VMFS cluster file system itself. As stated above, when deleting files(or a virtual disk or machine), the space that it was using - becomes dead space. But the array does not see these actions(the deletion) and does not release the blocks.
  • The guest file system. Dead space accumulates when data is deleted from the guest server, while the array is also not able to perceive this.

Reclaim space in VMware

The UNMAP command is used for dead space reclamation. But this command is an automatic since ESXi 5.0 and vSphere 6.5 only. In the previous versions, UNMAP was performed as manual process.

Can you do VMFS Recovery? Yes!

You don’t even have to think about it; with DiskInternals VMFS Recovery, you will have the best, most professional software tool on the Internet. In addition, you will only need to purchase a license if you want to export data; all other functions are free. The program recovers any information you are interested in from damaged or serviceable disks in VMFS format and returns VMDK files. The program is guaranteed to support file names and multilevel Unicode folders. All actions will be coordinated with the Recovery Wizard so that you will not be left to figure out the application on your own.

Instructions for using this application:

After successfully downloading and installing DiskInternals VMFS Recovery, you can begin.

First, connect via SSH. If this is not necessary, then skip this step.

Then, open the local drive or SSH drive.

After scanning, find the desired VMDK files.

Then mount the VMDK file and open it.

Preview the found files, for free.

The application will do everything necessary to recover files for you.

After that, you will need a license to export data.

You should export data to a trusted and reliable source in order to prevent damage and loss of data in the future.

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