Symptoms:

• When taking a backup of the large vmdk file, vCenter Server goes into unresponsive state.
• Map Disk Region events are generated continuously.

When you take a backup of the vmdk file using the SAN transport mode, Map Disk Region call is initiated by VDDK to obtain the mapping of the disk. If disk is large or highly fragmented, multiple calls are initiated to obtain the mapping across the disk. Every time a call is initiated, vCenter Server events get updated with the call info as Map Disk Region. vCenter Server database is filled with Map Disk Region events and vCenter Server becomes unresponsive.