On Sun, June 21, 2009 12:21 am, Ralf Müller wrote: > > Am 19.06.2009 um 03:58 schrieb Neil Brown: >>>> When you added it back the event counter would differ and the >>>> disk needs to be resynced completly. A bitmap would help limiting >>>> this >>>> to the parts that have changed. Add an internal bitmap before you >>>> remove the next disk. >>> >>> There is an internal write intent bitmap at the array: >>> DatenGrab:/media # cat /proc/mdstat >>> Personalities : [raid6] [raid5] [raid4] [raid1] >>> md3 : active raid5 sdf1[3] sdi1[0] sdj1[4] sdh1[1] >>> 3457099008 blocks super 1.2 level 5, 256k chunk, algorithm 2 >>> [4/4] [UUUU] >>> bitmap: 0/275 pages [0KB], 2048KB chunk >>> >>> Do you have an idea why this bitmap has been ignored? >> >> Probably a kernel bug. There have been a couple of fixes relating to >> this since 2.6.25. Hopefully it is all working in 2.6.30... >> >> The bug that you hit was probably the one fixed by >> commit a0da84f35b25875870270d16b6eccda4884d61a7 >> which is in 2.6.27. > > Just for your information: I updated to OpenSuSE 11.1 > (kernel 2.6.27.23-0.1) and tried to remove, grow, re-add the other > devices. For the first disk it worked - re-add took nearly no time > because of the bitmap. For the second disk - it did not work: complete > resync triggered. No idea why. It has been the same sequence of > commands on the same kind of device. There were no filesystem write > operations on the raid while updating. Thanks for keeping us informed. The was another bug related to this that was fixed much more recently - in 2.6.30 I think. commit d0a4bb492772ce5c4bdfba3744a99ed6f6fb238f I think it was a lot harder to hit, but maybe you hit it. > > I will wait for the resync to complete, offline the array, grow the > last device and reassemble with "--update=devicesize". Would there > have been a way to update the recorded device-size of the member > devices online? If the fail/grow/re-add cycle would have worked, I > still would have superblocks with the old size - right? With a recent kernel, you can write "0" (or some other size in sectors) to /sys/block/mdX/md/dev-YYY/size, and it will update the device size online. That functionality appeared in 2.6.26 so OpenSUSE 11.1 should have it. Yes - after fail/grow/re-add, the size recored in the metadata is unchanged. You need to increase the size on each device as described above or with --update=devicesize during assemble, then update the size of the array using "mdadm --grow --size=max /dev/mdX". NeilBrown -- 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
