When a new datastore is created in VMware vSphere an error message is shown in the vSphere Client showing
“Call “HostDatastoreSystem.CreateVmfsDatastore” for object “ha-datastoresystem” on ESXi “hostname” failed.
Operation failed, diagnostics report: Unable to create Filesystem, please see VMkernel log for more details: Function not implemented”
This error can be caused by several situations:
if storage is accessed over iSCSI: MTU size is not set correctly one on of the components
Make sure all networking components are set to an MTU of the same size: the virtual switch properties, the vmkernel ports used for the iSCSI traffic, physical switch, storage device . If have seen this error while trying to create a datastore on a Iomega device iSCSI LUN because the virtual switch MTU was set at 1500.
There has been a situation in which the Dell switch MTU setting needed to be higher than the MTU size on the surrounding infrastructure. So: vSwitch, VMKernel and EqualLogic mtu: 9000. 6224′s: 9126
read more in this blogpost.
If the storage has been used before for other purposes.
Another reason could be the volume has been formated using a filesystem which is not compatible with the VMware vSphere version. If possible delete the LUN and recreate.
check this VMware knowledgebase article.
Or check out this VMware KB article Unable to add a deleted local datastore back to the ESXi 5.0 host