Dear list, I am seeing a strange performance issue on a 4 x 4TB md raid6 on kernel 3.12. Initial resync goes nice and fast at 130MB/s: > # cat /proc/mdstat > Personalities : [raid1] [raid6] [raid5] [raid4] > md1 : active raid6 sda3[0] sdd3[3] sdc3[2] sdb3[1] > 7751269376 blocks super 1.2 level 6, 512k chunk, algorithm 2 [4/4] [UUUU] > [=>...................] resync = 7.5% (293925504/3875634688) finish=458.4min speed=130210K/sec > > md0 : active raid1 sda2[0] sdd2[3] sdc2[2] sdb2[1] > 29280128 blocks super 1.2 [4/4] [UUUU] > > unused devices: <none> ...unless the ext4 filesystem on the array is mounted read-write! Then, speed plummets to 1 - 7MB/s. The filesystem is empty and totally idle; a simple "mount -o remount,ro" restores the speed to 130MB/s. I dumped the /sys/block/md1/md tree with the filesystem mounted ro and rw, the diff looks like this: > # diff -u md.rw md.ro > [...] > --- md.rw/stripe_cache_active 2014-02-25 17:33:31.250019324 +0100 > +++ md.ro/stripe_cache_active 2014-02-25 17:33:31.250019324 +0100 > @@ -1 +1 @@ > -0 > +256 > diff -u md.rw/sync_speed md.ro/sync_speed > --- md.rw/sync_speed 2014-02-25 17:33:31.250019324 +0100 > +++ md.ro/sync_speed 2014-02-25 17:33:31.250019324 +0100 > @@ -1 +1 @@ > -1052 > +126244 So, stripe_cache_active is zero if the fs is mounted rw. Hmm. Interestingly, if I increase sync_speed_min to 100MB/s, I do get 100MB/s. Any idea what is going on? Best regards, Jakob Unterwurzacher -- 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
