If your datastore was formatted with VMFS2, you must first upgrade it to VMFS3. Because ESXi 5.x hosts cannot access VMFS2 datastores, use a legacy host, ESX/ESXi 4.x or earlier, to access the VMFS2 datastore and perform the VMFS2 to VMFS3 upgrade.
Commit or discard any changes to virtual disks in the VMFS2 datastore that you plan to upgrade.
Back up the VMFS2 datastore.
Be sure that no powered on virtual machines are using the VMFS2 datastore.
Be sure that no other ESXi host is accessing the VMFS2 datastore.
To upgrade the VMFS2 file system, its file block size must not exceed 8MB.
- Log in to the vSphere Client, and select a host from the inventory panel.
- Click the Configuration tab and click Storage.
- Select the datastore that uses the VMFS2 format.
- Click Upgrade to VMFS3.
- Perform a rescan on all hosts that see the datastore.
What to do next
After you upgrade your VMFS2 datastore to VMFS3, the datastore becomes available on the ESXi 5.x host. You can now use the ESXi 5.x host to complete the process of upgrading to VMFS5.