With the installation of VMware ESXi 4, data stores will automatically be created using the default settings. This includes a block size of 1 MB. If you don't want that, you could delete the empty datastore and create a new one.

Sometimes, deleting the empty datastore fails with the message:

Quote

Call "HostDatastoreSystem.RemoveDatastore" for object "ha-datastoresystem" on ESXi "xx.xx.xx.xx" failed.

VMware's KB 1017104 provides the solution for another problem, but this works just as well with this issue, with a little variation.

Notice

Performing the steps in this solution will totally utterly destroy your data store. Do not use it if there's still any required data left on the store!!

The steps to resolve are:

1. First, look up the naa ID of the disk using the vSphere client (Configuration, Storage).
2. Log in using SSH (enable Remote Technical Support), or iLO/IMM/console.
3. Run the command to verify the naa ID of the disk:

esxcfg-scsidevs –l | grep –I naa

4. Run the fdisk utility to delete the partitions:

fdisk /vmfs/devices/disks/naa.<number>

5. Press d, then select partition 1.
   Do the same for partition 2 and 3 until all partitions are gone. Type w, then Enter to write out the partition layout. The following message is shown:

The partition table has been altered!

6. Reload the vmfs by running the following command:

vmkfstools -V

7. Refresh the vSphere Client GUI. Although the data store will still be present, you will now be able to delete it.

After it's gone, you can recreate a new datastore. Note that traces of the partitions will still be present. When creating the store, select to use all free space. This will get rid of the remnants of the previous partitions.