On Sat, 5 Feb 2011 18:33:34 +0100 Piergiorgio Sartor <piergiorgio.sartor@xxxxxxxx> wrote: > > Look in the mdadm source code, particularly at restripe.c > > > > Also > > make test_stripe > > > > make a program the the test suite uses for verify data correctness. > > > > That should give you enough hints to get you started. > > Hi Neil, > > I'm trying to use the "test_stripe" binary, just to > confirm the operation, in test mode (no save nor restore). > > Unfortunately, it seems not work properly, in my hands. > > I created a 4 disks RAID-6 (/dev/loop[0-3]), with: > > mdadm -C /dev/md111 -l 6 -n 4 --chunk=64 /dev/loop[0-3] > > Filled the array from urandom: > > dd if=/dev/urandom of=/dev/md111 > > And tried: > > ./test_stripe test file_test.raw 4 65536 6 2 65536 $[ 65536 * 3 ] /dev/loop[0-3] > > This returns: > > 0->0 > 1->1 > P(2) wrong at 1 > Q(3) wrong at 1 > 0->3 > 1->0 > P(1) wrong at 2 > Q(2) wrong at 2 > 0->2 > 1->3 > P(0) wrong at 3 > Q(1) wrong at 3 > > The array filled with "0" does not return any error. > > Am'I missing something or the code has problems? > > An other question, I noticed the code uses an array of > "offsets" which seem to be filled with "0" and never > changed. > Is this really wanted? > Is the offset information the one found per component > using "mdadm -E ..." or /sys/class/block/mdX/md/rdX/offset? > What's the relation with the "start" parameter of "test_stripe"? > > Thanks in advance for any hints or suggestions. test_stripe assumes that the data starts at the start of each device. AS you are using 1.2 metadata (the default), data starts about 1M in to the device (I think - you can check with --examine) You could fix test_stripe to put the right value in the 'offsets' array, or you could create the array with 1.0 or 0.90 metadata. NeilBrown > > The md device is: > > /dev/md111: > Version : 1.2 > Creation Time : Sat Feb 5 17:48:49 2011 > Raid Level : raid6 > Array Size : 524160 (511.96 MiB 536.74 MB) > Used Dev Size : 262080 (255.98 MiB 268.37 MB) > Raid Devices : 4 > Total Devices : 4 > Persistence : Superblock is persistent > > Update Time : Sat Feb 5 18:19:45 2011 > State : clean > Active Devices : 4 > Working Devices : 4 > Failed Devices : 0 > Spare Devices : 0 > > Layout : left-symmetric > Chunk Size : 64K > > Name : lazy.lzy:111 (local to host lazy.lzy) > UUID : b794fb80:c4006853:47761570:3d97a1d2 > Events : 42 > > Number Major Minor RaidDevice State > 0 7 0 0 active sync /dev/loop0 > 1 7 1 1 active sync /dev/loop1 > 2 7 2 2 active sync /dev/loop2 > 3 7 3 3 active sync /dev/loop3 > > bye, > -- 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
