If this is an RDM, so the LUN is mapped to a single virtual machine then you can make the ESXi host have access to the LUN but the mapping is only for that specific VM.
But if you have mapped the LUN to the first ESXi host and are seeing a datastore in the management GUI then you should have no problem with mapping that same VMFS volume to the second ESXi host.
This needs to be done in the Dell MD management panel.
You just need to add the host in the correct Mapping group. Can be the default one or a new one you have created for that LUN.
Hope this helps
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