Space Efficient Virtual Disk is a new virtual disk (vmdk) format. It is a sparse format similar to redo log based disk with the added benefit of both growing and shrinking dynamically. This new vmdk format is applicable to both block based storage (iSCSI, FC etc.,) and file based storage (NFS). The block size of these disks is 4KB that aligns well with the NTFS block size and provides maximum space efficiency. In addition, it helps keep IOs aligned on most storage arrays .

Note :- Virtual Device Node can be SCSI also .

We have to convert the sparse disk using the vmkfstools command. 

To do this perform the following steps:

1. SSH onto the ESX server and navigate to the folder containing the vmdk file in sparse format.

2. Run the following command to convert VM1.vmdk to VM1-thick.vmdk:

3. Once it completes remove the old sparse disk from virtual machine by using edit option .

4.Add the newly created thick disk, which is VM1-thick.vmdk, to the VM. You will now see that the format of the disk has changed to thick:

Note :- Virtual Device Node can be SCSI also .

4. Power on the VM and ensure it is working properly.