One of the issues that I have run into in the past when working with iscsi disks occurs when a host (initiator) is unable to logout gracefully from an iscsi disk when attempting to shutdown or reboot a host. Note that this is a known issue and is documented here and here. I have not read completely through the RHEL 6 Bugzilla to see if the issue has been resolved, however I can tell you that I have seen this issue in RHEL 6.2.
filesystem
RHEL6 – Quick and Dirty NFS How To
So if you are reading this you many not be aware of the fact that I already put up a post on NFS on RHEL6 (you can find it here). However that post is basically just a redirect to another blog post that I ran into on the subject. And despite the fact that its very well written, and has no apparent spelling mistakes, or inapropriate comments about NFS, I felt the need to draft my own post. At this point I really cannot seem to remember anything technical if I don't put up a blog post on the subject. After all I have been doing so for over 4 years, so why stop now.