On Wednesday 27 August 2003 11.32, Andres Kroonmaa wrote: > Isn't block io restricted to 4/8K size anyway? Its a matter of VM > of OS.
Depends.. raw disk block via character device is usually 512. VM or OS may put additional page restrictions on filesystem or block device I/O where page size is determined by CPU and OS architecture (usually 4-16KB) > By using raw device or O_DIRECT it becomes responsibility of app > to ensure optimal disk access pattern. > Now that ram has become cheap and huge disk systems fast, need for > apps handling additional complexity is hard to justify. Agreed in principle. > COSS, being basically ring buffer, is very simple disk pattern and > doesn't really benefit much from avoiding OS support, so, imo, it > would work as well on plain FS as on any other approach. The only > reason to go for raw disk or O_DIRECT would be if we want to keep > ram usage to very minimum, ie for very lowend boxes. And most OS:es can be tuned accordingly to not waste valuable memory on filesystem buffers when memory is limited, and the OS algorithms becomes smarter and smarter requiring less such tuning. Regards Henrik
