Modern kernels use a better strategy for writing cached disk blocks. In addition to the kernel changes, this involves replacing the old update program which used to write everything every 30 seconds with a more subtle daemon (actually a pair), known as bdflush. Get bdflush-n.n.tar.gz from the same place as the kernel source code ("How To Upgrade/Recompile a Kernel.") and compile and install it. bdflush should be started before the usual boot-time file system checks. It will work fine with older kernels as well, so there's no need to keep the old update around.