>> See my reply to nate. If you are using boards with 12GB of cache, >> software raid is not even on the radar. >> > > True, but I feel an important point is being missed here. > > In order to avoid a lot of the random I/O file systems use page cache > to combine I/O operations and transaction logs to log it sequentially > before committing it in the background later but the ability of the > disks to handle a large amount of random I/O is also a big factor as > if the commits can't execute fast enough the log will not empty enough > to make it perform, so then you need an ever bigger log. > > /me shrugs. It is not as if a hardware raid card is the only solution. One can try external journaling devices for the filesystem like a Gigabyte I-RAM drive or a UMEM card and still use md devices. Although I would not bother with a software raid setup if I had lots of disk arrays I suspect.