I just upgrading my VMware ESXi 5.0 to VMware ESXi 5.1 using installation disc and I found one of my VM inside this machine cannot be started using vSphere client with following error:
Cannot open the disk '/vmfs/volumes/4a365b5d-eceda119-439b-000cfc0086f3/examplevm/examplevm-000002.vmdk' or one of the snapshot disks it depends on.
Further troubleshooting required me to SSH into the ESXi host and analyze the vmware.log under datastore for this VM and I found following error:
DISKLIB-CHAINESX : ChainESXOpenSubChainNode: can't create multiextent node 6b8b4567-MyServer-flat001.vmdk failed with error The system cannot find the file specified (0xbad0003, Not found)
It turn out that the multiextent module is not loaded inside ESXi 5.1 and following command fix my problem:
$ vmkload_mod multiextent Module multiextent loaded successfully
Add the command into /etc/rc.local.d/local.sh to make sure it will auto start on boot:
Once done, try to turn on the VM once again using vSphere client.