VMFS-4 on ESXi 5 and RDM

[Titans99]

Hi, I have two ESXi 4.1 hosts and I just introduced an ESXi 5 host to the mix (iSCSI SAN).  All hosts can see all LUN's.  I wanted to test presenting a new 4TB physical RDM LUN to an exisiting VM, but when I try to do so, I get the message "Mappings for LUNs with capacity greater than 2TB can be stored on VMFS5 datastores only"

1. Do I need to upgrade the ESXi 4.1 hosts first?
2. Will upgrading convert the iSCSI VMFS-4 datastores to VMFS-5?
3. Will it hurt anything to have the VMFS-4 datastores presented an ESXi 5 host
4. Just to clarify, physical RDM disks over 2TB are now supported in ESXi 5 - correct?

Thank you for your assistance.  I'm about to purchase VMware Essentianl by the way.

[Dave_Mishchenko · Accepted solution]

Do I need to upgrade the ESXi 4.1 hosts first?

     - No - you could do this with the existing configuration, but the VM would be limited to running on just the ESXi 5 host.  You would have to create a new datastore, present it to the ESXi 5 host and create a vmfs5 datastore.

Will upgrading convert the iSCSI VMFS-4 datastores to VMFS-5?

     - No - upgrading is a manual step you perform on the datastore.

Will it hurt anything to have the VMFS-4 datastores presented an ESXi 5 host

     - There's no problem doing this.   If the VM stays at hardware version 7 you can run the VM on either ESXi 4 or 5.  Once you upgrade the hardware version for the VM it can only run on the ESXi 5 host.

Just to clarify, physical RDM disks over 2TB are now supported in ESXi 5 - correct?

       - Yes - physical RDMs and datastores can exceed 2 TB.   Virtual disks and virtual RDMs are limited still to 2 TB.

[Titans99]

So to accomplish adding the 4TB RDM to the VM, in this case I would need to either create a new datastore from the ESXi 5 host, then move the exisitng VM over to it, or upgrade the existing VMFS-4 datastores to VMFS-5 (knowing they can only run on ESXi 5) .... is this correct?  Thanks!

[a_p_]

Yes, VMFS-5 is only supported with ESXi 5.0 hosts.

Btw. There is no VMFS-4. It's either VMFS-3 or VMFS-5.

André