These documents should help you:
Investigating disk space on an ESX host
To get the total look at the /vmfs/devices line for the vdf -h command
http://kb.vmware.com/kb/1003564
Using esxtop to identify storage performance issues
Using the disk screen in esxtop to expand the CID, TID, and LID to determine the amount of I/O that a virtual machine (WID) is using
Basic SCSI Storage Troubleshooting
Contact support if you need help.
Hanna
Hope that helps,
Hanna
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BSCS, VCP2, VCP VI3, VCP vSphere, VCP 5
https://www.ibm.com/developerworks/mydeveloperworks/blogs/vmware-support-ibm