Based on the error message, 4096 should also fail. Guy -----Original Message----- From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Brad Campbell Sent: Thursday, August 26, 2004 5:55 AM To: Daniel Pittman Cc: linux-raid@xxxxxxxxxxxxxxx Subject: Re: Raid-0 speed Daniel Pittman wrote: >>With the raid-0 running, doing a dd if=/dev/md1 of=/dev/null I get about >> 55MB/s read speed. >> >>I can't quite figure out why the md is so slow. Given its using >>streaming reads with no seeking it should be over 100MB/s. > > > Your chunk size is way to low to give good streaming reads. The kernel > needs to switch between devices every 128 kilobytes, while is rather > low. > > Try slowly pushing the chunk size to 16384 and see when your performance > gets back up to your expected level. Nope.. Any chunk size > 4096 gives me too big chunk_size: 8388608 > 4194303. And the performance difference between chunk=16 and chunk=4096 is less than 5MB/s --chunk=16 gives me 48.43 MB/s --chunk=4096 gives me 51.52 MB/s Regards, Brad - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
