Hello, We have an ESX 4.0 cluster with 2 hosts, EMC Clarion SAN storage with 10 LUNs. We have added 2 new 400 GB LUNs. All the LUNs are visible from both hosts. I have extended an existing 500 GB datastore with one of these 400 GB LUNs - the new datastore size is now 900 GB. I'd like to do the same operation with the second 400 GB LUN to extend another existing datastore but I'm not able to do it. The LUN is available to create a brand new datastore but is not visible to extend an existing one. I don't understand why everything was fine with the other one and why can't I do the same exact operation with this LUN. The result is the same on both hosts. The SAN admin have erased and re-created several times this LUN. I have rescan the HBA each time. In attachment you can find the result of the esxcfg-mpath -l and fdisk -l commands on both servers. Does somebody have an idea please?