I am having Slow IO performance issue in Oracle Linux 5.8 uek 64bit kernel for SATA Disk connected via SAN,
and I have tried using dm-multipath and LVM, nep,
and the same SATA disk does not have any issue with RHEL5.8 32bit, with RMAN Backup it is 8-9 hours backup duration,
but in OEL5.8 64bit uek it takes 15Hours to complete RMAN Backup of Oracle R12 DB Backup.
Tools like iostat or others measure the workload and can not determine whether or not any running task or configuration is done properly or working as efficently as advertised. Performance tuning of Oracle database, including RMAN is certainly beyond the scope of this forum.
You can do a simple benchmark to measure the data throughput of your storage device. When you run the tests from different systems or kernels it should give you an idea what to expect. For instance:
The Oracle UEK x86-64 bit kernel should not slow down your disk access. If it does, then there are unusual compatibility issues or other unusual reasons. Based on your description I have no idea what hardware or I/O interface you are using.
Performance statistics and statements that disk access is faster in a previous or other version of the Linux kernel is not useful for troubleshooting. I suggest to check the vendor support pages of your disk/adapter subsystem to see if there are any firmware updates or other related information available.
Please contact Oracle support. Participation in this forum is on a voluntary basis. As such you are not in a position to request any official driver software or a solution from me for your HW configuration. I don't even have to reply to your post if I don't feel like it. If you need help for a production system, getting an Oracle Linux support subscription might be your best option.
Looking at your problem again, I wonder what records exist that point to an issue with the Oracle Linux kernel or driver. To find out what driver you are using, you can use the "lspci -v" command and filter out the information of the appropriate HBA controller.
If this is indeed a problem of using a 64-bit or 32-bit driver, I suggest to check the vendor support page (IBM) to see if there is a know issue. Perhaps your SAN or HBA controller or PC BIOS firmware requires a patch for 64-bit compatiblity. And again, to find out if it is a problem with the Oracle UEK kernel, simply boot the system using the RHEL kernel. A problem with the multipath configuration may causes the system to use a drive different than you expect, but afaik multipath does not provide the actual device driver to affect data throughput I/O, nor does LVM.