In a lot of ESX/ESXi implementations I noticed some common warnings messages in the VMkernel log. I wanted to get more insight into these warnings so I contacted VMware support for some explanation. Here are my results:
WARNING: UserCartel: 1820: Fork not supported for multithreaded parents
This message is normally caused by a known bug in qlogic drivers. VMware can’t provide an exact cause as they are still waiting for qlogic to come back with an updated driver but there is no cause for concern, no impact on the system has been demonstrated.
WARNING: UserLinux: 1717: UNIMPLEMENTED! write-back of mmap regions unsupported
This message is caused problem in the CIM agent in combination with the OEM providers and some IHV information that is reported whether the Hardware exists or not on the host. This problem can result in the error generated. The message can be ignored for the moment and will be fixed in a future patch.
WARNING: VFAT: 154: File_Ioctl
The messages is not a cause for concern. There messages are being created by busybox. Despite the ‘warning’ tag they are actually information and are being generated as busybox interacts with parts of the filesystem. There is an upcoming patch due which will stop the messages from being logged.