I had an issue with performing vMotion. Many times, but not always when I entered maintenance mode on one of the vSphere 6,5 hosts, vMotion process was stuck, halted, pauzed at 21 %. When I selected a number of VM’s and did a vMotion in many cases the vMotion went fine.
The error presented in vCenter Server was ” Failed waiting for data. Error 195887137 . Timeout. vMotion migration failed to send buffer to remote host. Failed writinh stream completion.
The logfile did not produce anything which could help. Browsing through some KB articles many times wrong sized MTU size was mentioned as a cause.
So I had a look at the distributed swith. Indeed the MTU size of the VMkernel for vMotion was set at 9000 while the port of the physical switch was at 1500.
So always check if vmkernel, virtual switch of vSphere and the physical switch port have the same value for MTU.
Another error text was “the vMotion failed bacause the destination host did not receive data from the source host on the vMotion network. Failed to initialize migration at source. Error 195887109