Thank you for information.
I have investigated it further and for sure the biggest impact is toward database performance. One of my application's use case is uploading and downloding files and these are rather big files.
The upload and download is realized over web service deployed on JBoss server. This is not perfect architecture, however it is as it is. I see that transfer of files is impacting database a lot. I suspect that any JBoss operation on temp, data and log directories might be affected.
Thanks
Łukasz