Hello - I am in the process of testing ESXi and all the applications we have work well except for one, The application we are having performance issues with is MongoDB (http://www.mongodb.org) and it uses mmap files to maintain document storage. The performance of the application running on a guest Linux OS is easily 75% slower then running on a Linux laptop (no virtualization). Using vmstat and iostat we are seeing 50% iowait on the guest. The host has 12GB of RAM and is dual quad core so there are plenty of resources. My thought is that the use of mmap by the MongoDB application causes huge problems for ESXi. The way the application works is based on memory mapping a few 2 GB files and then accessing these files / updating these files by reading / updating the memory map. Every 10 seconds the application calls an fsync to sync the files.
Does anyone have any tuning suggestions on this ?
I have searched the forums and there are no issues reported for mmap on Linux but it is also not a common use case.
