Eyal Lebedinsky wrote:
Executive summary: it is not the TX4. It is not really raidreconf. You must specify the parity-algorithm in raidtab because the raidreconf default is not what one expects. I have now investigated the corrupted 3->4 disk raidreconf and I can see that there is a pattern to the problem. A similar pattern is seen with a 4->5 run. I wrote known values to the raid before the reconf and checked after. The process is create /dev/md0 write to it raidreconf it read it and see which blocks show up where What I see is that the 2nd pair of each 6 blocks is swapped. Here is the error list for a test with 1 cyl (31 blocks) per disk: bad block 2 says it is 3 bad block 3 says it is 2 bad block 8 says it is 9 bad block 9 says it is 8 bad block 14 says it is 15 bad block 15 says it is 14 bad block 20 says it is 21 bad block 21 says it is 20 bad block 26 says it is 27 bad block 27 says it is 26 bad block 32 says it is 33 bad block 33 says it is 32 bad block 38 says it is 39 bad block 39 says it is 38 bad block 44 says it is 45 bad block 45 says it is 44 bad block 50 says it is 51 bad block 51 says it is 50 bad block 56 says it is 57 bad block 57 says it is 56 20 errors in 62 blocks At this point I decided that I must take the TX4 out of the equation. This is just too regular for a hardware problem. I created four partitions on one disk and repeated the test. It failed just the same. I was now reasonably convinced that it is raidreconf that gives me grief. Nevertheless, the pattern is just too regular. Maybe the program does not agree with md on the parity algorithm? The default is said to be left-symmetric (see man mdadm; man raidtab does not say), so I specified this explicitly in the raidtab and it started working. Good, but I needed to understand this. Looking at the raidtools code (where raidreconf is built), I think that it does not default to left-symmetric. It looks to me like the config struct is malloced and zeroed (with memset) meaning the .layout member is set to left-asymmetric (see top of parser.c) and I do not see that it is ever set to any other default (left-symmetric would be numeric 2). -- Eyal Lebedinsky (eyal@xxxxxxxxxxxxxx) <http://samba.org/eyal/> attach .zip as .dat - 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
Nice work Eyal :) Now all we need is a patch for raid-reconf to fix default behaviour? :D Regards, Tyler. -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.1/104 - Release Date: 9/16/2005 - 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
