VMWare ESXi slow file copy to guest

Java tends to confuse the VMWare memory management systems, as it adds yet another layer of memory management.

There is a KB article, linked below. But the key one is to size the reserved VM memory (not just the VM memory size) to be >= to the memory of Java (tomcat).

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1008480

I got explanation from guys on VMWare forum in thread http://communities.vmware.com/message/2012333 . And the reason is that ESXi does no caching and completely relies on the controller for writing data to disks so speed 20MB/s with write-through cache mode (only mode this controller supports as it does not have BBU) is standard. Hyper-V is apparently doing some caching on OS level (which is not so safe on power failure/system crash) and so it can achieve much higher speed. Other controller with write-back cache should be able to achieve about 90MB/s.