On 05/07/2012 01:34 PM, Sebastian Riemer wrote: > On 07/05/12 13:18, NeilBrown wrote: >> You didn't say which kernel you are running. >> >> However md/raid1 bases all those settings on the minimum or maximum (as >> appropriate) of the setting of the underlying devices, using blk_stack_limits >> (in block/blk-settings.c). >> >> So the likely answer is that one of your HDDs has a smaller max_sectors_kb? >> >> NeilBrown > > Thanks for your answer! Kernel version is vanilla 3.2, but I've also > tested 2.6.32. There is no difference. Distribution: Debian Squeeze. > > I can even reproduce this behaviour with RAM disks: > > # modprobe brd rd_nr=2 rd_size=1048576 > # cat /sys/block/ram0/queue/max_sectors_kb > 512 > # cat /sys/block/ram1/queue/max_sectors_kb > 512 > # mdadm -C /dev/md200 --force --assume-clean -n 2 -l raid1 -a md > /dev/ram0 /dev/ram1 > # cat /sys/block/md200/queue/max_sectors_kb > 127 > > I'll have a look at that blk_stack_limits() function. > I think you need something like this. I thought there already went something in in recent kernel, will check it later on today. Index: 2.6.32.13/drivers/md/raid0.c =================================================================== --- 2.6.32.13.orig/drivers/md/raid0.c +++ 2.6.32.13/drivers/md/raid0.c @@ -96,6 +96,7 @@ static int create_strip_zones(mddev_t *m int cnt; char b[BDEVNAME_SIZE]; raid0_conf_t *conf = kzalloc(sizeof(*conf), GFP_KERNEL); + unsigned int opt_io_size; if (!conf) return -ENOMEM; @@ -256,9 +257,16 @@ static int create_strip_zones(mddev_t *m goto abort; } + /* + * To send large IOs to the drives we need sufficient segments + * for our own queue first. + */ + opt_io_size = (mddev->chunk_sectors << 9) * mddev->raid_disks; + blk_queue_max_phys_segments(mddev->queue, opt_io_size >> PAGE_SHIFT); + blk_queue_max_hw_segments(mddev->queue, opt_io_size >> PAGE_SHIFT); + blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9); - blk_queue_io_opt(mddev->queue, - (mddev->chunk_sectors << 9) * mddev->raid_disks); + blk_queue_io_opt(mddev->queue, opt_io_size); printk(KERN_INFO "raid0: done.\n"); mddev->private = conf; Cheers, Bernd -- 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
