bigpcman wrote:Seems to me the linux kernel uses a disk file cache to speed up disk access. Am I missing something here?
Linux file system (i.e. extfs2/3, reiserfs etc.) is a caching file system, but caching does not take place on file level, but (one layer beyond) on block level. A block is the smallest unit of disk I/O. Block size depends on disk size and number of blocks, it is determined during disk format ("mkfs" command in linux/unix).
The cache is builtin in the file system driver, i.e. in the linux kernel. You cannot configure or modify it, it is used automatically.
As I am not really a fan of stacked cachings (usually the most powerfull caching is done by the OS), i dont think that there is a measurable performance gain by using several stacking algorithms at different levels/layers. You should run some benchmarks on your system to find out, if additional caching really raises performanceof your webserver.