I came across an error recently and thought I would share my solution.
While configuring an iSCSI based vSphere 4 implementation I came across the following error when I went to create a VMFS volume on a LUN that I had just presented and discovered.
“Unable to create File system, please see VMkernel log for more details”. I took a look at the log but could decipher the messages.
I had configured everything to use jumbo frames including the physical switches (or so I thought) and I could not get it to work. I could see the LUN and all the paths to the LUN but could not create a VMFS volume. After changing everything back to the standard 1500 MTU everything worked like a charm.
After double checking everything it turned out that the network guy had not enabled jumbo frames on the switch ports, even though he assured me he had! So I asked him to make the changes and I changed everything back to Jumbo frames again on the VMware side (VMKernel ports and the vSwitch etc.)
Once that was done I could create my VMFS volume and it’s been working great ever since.
It was odd that I could “see” the storage and presented LUNS with a misconfigured network but I could not “use” it until everything was spot on.