> As I understand it, it reads "chunksize" blocks from one drive, then > switches to the other drive, then back again. > > Try a bigger read - eg: > > time dd if=/dev/md6 of=/dev/null bs=128K count=8192 > > but I don't think there are any real gains to be made with RAID-1 - your > results more or less track everything I've seen and used with RAID-1 - ie. > disk read speed is the same as reading from a single device, and never > significantly faster. Actually I have managed to get about 30-40% higher throughput with just a little hacking on the code that selects what disk to use. Problem is -It selects the disk that is closest to the wanted sector by remembering what sector was last requested and what disk was used for it. -For sequential reads (sucha as hdparm) it will override and use the same disk anyways. (sector = lastsector+1) I gained a lot of throughput by alternating disk, but seek time was roughly doubled. I also tried to get smart and played some with the code in order to avoid seeking both disks back and forth wildly when there were two sequential reads. I didn't find a good way to do it unfortunately. I'm not going to make any patch available, because I removed bad-disk checking in order to simplify it. -HK - 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
