Discovered something, you can get weird behaviour on oracle R11.07 rac if you have system on a slower filesystem. we have discovered that a LUN confugured with a slower SYSTEM tablespace gave the database funny behaviours. And of course gave R12.1 funnier behaviours. Transactions not completing..select count(*) from obj took ten minutes etc. So, when you create a SAN be careful on how the file system is created, use RAD10 or RAID5 only (or others with stripping option).
Another hint, upgrade OCFS to latest version, but be warned ocfs version must be same as the kernel version. uname -a for kernel version and rpm -qa | grep ocfs for ocfs.
good luck..it took us ages to get that one right.