I totally meant to get this out a few days ago but am now finally catching up. During the beta testing period, I had all kinds of problems getting 5.1 working. Come to find out, Synology DSM is not compatible with vSphere 5.1 with BOTH iSCSI and NFS. I HAVE NOT had a chance to test the GA version, but build 732143 which is a beta build along with the beta of DSM 4.1, experienced this issue. This has also been confirmed by Jason Nash and Jeremiah Dooley, so I know it's not just me.
It's possible to mount both NFS and iSCSI datastores, but when you try to build or power on a VM, everything begins to halt when it needs to write to disk. If everything runs in memory (like mounting an ISO and beginning an OS installation) it looks like it's working, but when it comes to install the OS to disk, it begins to crawl. I checked the vmkernel log and here is what is shown. You can see that after I power on the VM, it gets binded to a port but when it tries to read from disk, there are all sorts of errors:Add a comment