Linux disk I/O performance issue -- what config options to look at?

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http://unix.stackexchange.com – We discovered an I/O related performance problem when using the default SLES11 SP2 kernel. Our same application on the same hardware had no issue with (the admittedly ancient SLES9 SP3). We had a feeling it has something to do with the kernel and have done the following experiment so far: Downloaded and unpacked the kernel.org 3.0.13 source tree. Installed Novell's kernel-source-3.0.13-0.27.1 package. This is the 3.0.13 source with all of Novell's patches/tweaks already applied. In the 3.0.13 tree did a make x86_64_defconfig to generate a default config file, then used make menuconfig to (HowTos)