There were problems that affected UEK and NFS when 18.104.22.168.1 was initially released (as covered by Andy Colvin). As mentioned in the comments of Andy’s post: Oracle released an updated ISO with fixes for this problem (patch 16432033).
There were also problems with kdump not functioning after 22.214.171.124.1 as listed in “Issue 1.17” of Oracle MOS “Exadata 126.96.36.199.1 release and patch (14522699) for Exadata 188.8.131.52, 184.108.40.206.x, 220.127.116.11.x, 18.104.22.168.x, 22.214.171.124.x, 126.96.36.199.x, 188.8.131.52.x (Doc ID 1485475.1)”.
After updating to 184.108.40.206.1 using the updated ISO (with NFS fixes) and installing the later version of kexec-tools as per the fix for “Issue 1.17” I was not able to get kdump to write to NFS during a crash.
I had previously tested kdump to NFS when running Exadata software version 220.127.116.11.2, so I knew that worked. 18.104.22.168.2 uses the RHEL kernel (“non-UEK” as Oracle would have you say) so I decided to test 22.214.171.124.1 after switching to the RHEL kernel, which also involves reverting the kexec-tools to the earlier version. That confirmed the issue was only evident when using UEK. Time for an SR…
Bug 17730336 – UNABLE TO KDUMP OVER NFS WITH KEXEC-TOOLS-2.0.3-3.0.4.EL5.X86_64.RPM INSTALLED
The bug listed above has been raised, but no fix has been supplied yet.
Not being able to direct kdump to NFS is probably not going to be your biggest worry, but definitely something to be aware of if you’re running UEK.
Note that I have only tested with 2.6.32-400.21.1el5uek. Oracle have confirmed they have reproduced the issue with 2.6.39-400.126.1.el5uek. Other UEK kernels may or may not be affected.