Neil Brown wrote: > > 1/ you didn't say how fast your SCSI buss is. I guess if it is > reasonably new it would be at least 80Mb/sec which should allow > 500 * 64K/s but it wouldn't have to be too old to not allow that, > and I don't like to assume things that aren't stated. > I should of specified that I am using ULTRA160... > 2/ You could be being slowed down by the stripe cache - it only > allows 256 concurrent 4k access. Try increasing NR_STRIPES at the > top of drivers/md/raid5.c - say to 2048. See if that makes a > difference. > This doesn't make any difference for 10 processes. I will increase the process number to see what happens. > 3/ Also, try applying > > >http://www.cse.unsw.edu.au/~neilb/patches/linux/2.4.3-pre6/patch-F-raid5readbypass > > This patch speeds up large sequential reads, at a possible small cost > to random read-modify-writes (I haven't measured any problems, but > haven't had the time to explore the performance thoroughly). > What it does is read directly into the filesystems buffer instead > of into the stripe cache and then memcpy into the filesys buffer. > Haven't tried this yet, when I do I will check the performance difference. > 4/ I'm assuming you are doing direct IO to /dev/md0. > Try making a mounting a filesystem of /dev/md0 first. This will > switch the device blocksize to 4K (if you have a 4k block size > filesystem). The larger block size improves performance > substantially. I always do I/O tests to a filesystem, not to the > block device, because it makes a difference and it is a filesystem > that I want to use (though I realise that you may not). > You are a legend. This did it!!! I am now getting the expected 500 random reads per second of 64K block data segments!!! If you are ever up on the Gold Coast, give me a call, and I will buy you a beer, or two, or three.... I am just really happy...:)))))))) Cheers, Kal. - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED]
