On Thu, Feb 18, 2010 at 10:47:55AM +1100, Neil Brown wrote: > On Tue, 16 Feb 2010 12:14:38 +0100 > Michael <michael@xxxxxxx> wrote: > > > On Tue, 16 Feb 2010 12:20:14 +1100, Neil Brown <neilb@xxxxxxx> wrote: > > >> is there any method to find that bad block in context of the raid block > > >> device? reading all files is not a good option on large raidsets. > > >> level 5, 64k chunk, algorithm 2 > > > > > > It isn't that hard. The code is in drivers/md/raid5.c in the > > kernel..... > > > > > > Rather than trying to describe in general, give me the block number, > > > device, > > > and "mdadm --examine" of that device, and I'll tell you how I get the > > > answer. > > > > > > the bad block number was 122060740 sec. > > > > [root@raw sqla]mdadm --examine /dev/sda3 > > /dev/sda3: > > Magic : a92b4efc > > Version : 0.91.00 > > UUID : 9815a2c6:c83a9a53:2a8015ce:9d8e5e8c (local to host raw) > > Creation Time : Thu Feb 11 16:01:12 2010 > > Raid Level : raid6 > > Used Dev Size : 966060672 (921.31 GiB 989.25 GB) > > Array Size : 2898182016 (2763.92 GiB 2967.74 GB) > > Raid Devices : 5 > > Total Devices : 5 > > Preferred Minor : 2 > > > > Reshape pos'n : 974014464 (928.89 GiB 997.39 GB) > > New Layout : left-symmetric > > > > Update Time : Tue Feb 16 11:58:37 2010 > > State : clean > > Active Devices : 5 > > Working Devices : 5 > > Failed Devices : 0 > > Spare Devices : 0 > > Checksum : 16372b12 - correct > > Events : 363519 > > > > Layout : left-symmetric-6 > > Chunk Size : 64K > > So... > There is no Data Offset give, so it is zero. so the block is 122060740 > sectors into the data area of the devices. > Chunksize if 64k (128 sectors), so > 122060740 / 128 == 953599 remainder 68. > So Stripe number 953599, and sector 68 of device '2' of that stripe. > > A stripe had 4 disks when raid5, 5 when raid6, so 3 data drives. > So stripe 953599 is 953599 * 3 * 128 sectors from the start of the > array. i.e. 366182016 sectors. > > In the raid5 layout: > 4 drives, so 4 different stripe layouts. > 953599 % 4 == 3, so it is layout 3 (of 0, 1, 2, 3). > Looking at the code in raid5.c for LEFT_SYMMETRIC > The parity disk is disk 0. The data disks follow that, > so device '2' holds data chunk '1'. > So we add 1 full chunk plus the 68 sectors of the partial chunk. > i.e. that sector is 366182016 + 128 + 68 > or sector 366182212 in the array. > > After the conversion to RAID6, there are 5 drives so 5 stripe layouts. > 953599 % 5 == 4, so layout 4 > So 'P' is device 0, 'Q' is device 1, D0 is device 2 etc. > So sda3 is the first data disk in the stripe, so there are no full stripes to > add, just the partial stripe. > 366182016 + 68 == 366182084 Sounds like it would be nice to have a program to calculate this :-) Seriously, Neil, would it be possible to lift out the code from the kernel to make a small utility - for salvaging raid file systems? best regards keld -- 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
