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RE: Power loss causes bad magic number??

To: "Eric Sandeen" <sandeen@xxxxxxxxxxx>
Subject: RE: Power loss causes bad magic number??
From: "Stephen Porter" <stephenp@xxxxxxxxxx>
Date: Wed, 16 Jul 2008 17:01:56 +1000
Cc: <xfs@xxxxxxxxxxx>
References: <F46A887185FC6044A7FAC577E31118AE022316C0@rsbne01.RSBNE.LOCAL> <487D5F80.1050909@sandeen.net>
Sender: xfs-bounce@xxxxxxxxxxx
Thread-index: Acjm7T9OK33lk02qRr6kulOVRdhfWQAIByci
Thread-topic: Power loss causes bad magic number??
Hi Eric,

It's not an in-kernel driver, I need to rebuild it each time the kernel is 
updated.

The output of the dd command follows:

$ sudo dd if=/dev/sdc bs=512 count=128 iflag=direct | hexdump -C | grep XFSB
128+0 records in
128+0 records out
65536 bytes (66 kB) copied, 0.0241381 s, 2.7 MB/s

I thought the XFSB marked the start of the superblock... and it not being there 
would be a Bad Thing??

without the "| grep XFSB" the output looks like:

$ sudo dd if=/dev/sdc bs=512 count=128 iflag=direct | hexdump -C
00000000  33 c0 8e d0 bc 00 7c fb  50 07 50 1f fc be 1b 7c  |3.....|.P.P....||
00000010  bf 1b 06 50 57 b9 e5 01  f3 a4 cb bd be 07 b1 04  |...PW...........|
00000020  38 6e 00 7c 09 75 13 83  c5 10 e2 f4 cd 18 8b f5  |8n.|.u..........|
00000030  83 c6 10 49 74 19 38 2c  74 f6 a0 b5 07 b4 07 8b  |...It.8,t.......|
00000040  f0 ac 3c 00 74 fc bb 07  00 b4 0e cd 10 eb f2 88  |..<.t...........|
00000050  4e 10 e8 46 00 73 2a fe  46 10 80 7e 04 0b 74 0b  |N..F.s*.F..~..t.|
00000060  80 7e 04 0c 74 05 a0 b6  07 75 d2 80 46 02 06 83  |.~..t....u..F...|
00000070  46 08 06 83 56 0a 00 e8  21 00 73 05 a0 b6 07 eb  |F...V...!.s.....|
00000080  bc 81 3e fe 7d 55 aa 74  0b 80 7e 10 00 74 c8 a0  |..>.}U.t..~..t..|
00000090  b7 07 eb a9 8b fc 1e 57  8b f5 cb bf 05 00 8a 56  |.......W.......V|
000000a0  00 b4 08 cd 13 72 23 8a  c1 24 3f 98 8a de 8a fc  |.....r#..$?.....|
000000b0  43 f7 e3 8b d1 86 d6 b1  06 d2 ee 42 f7 e2 39 56  |C..........B..9V|
000000c0  0a 77 23 72 05 39 46 08  73 1c b8 01 02 bb 00 7c  |.w#r.9F.s......||
000000d0  8b 4e 02 8b 56 00 cd 13  73 51 4f 74 4e 32 e4 8a  |.N..V...sQOtN2..|
000000e0  56 00 cd 13 eb e4 8a 56  00 60 bb aa 55 b4 41 cd  |V......V.`..U.A.|
000000f0  13 72 36 81 fb 55 aa 75  30 f6 c1 01 74 2b 61 60  |.r6..U.u0...t+a`|
00000100  6a 00 6a 00 ff 76 0a ff  76 08 6a 00 68 00 7c 6a  |j.j..v..v.j.h.|j|
00000110  01 6a 10 b4 42 8b f4 cd  13 61 61 73 0e 4f 74 0b  |.j..B....aas.Ot.|
00000120  32 e4 8a 56 00 cd 13 eb  d6 61 f9 c3 49 6e 76 61  |2..V.....a..Inva|
00000130  6c 69 64 20 70 61 72 74  69 74 69 6f 6e 20 74 61  |lid partition ta|
00000140  62 6c 65 00 45 72 72 6f  72 20 6c 6f 61 64 69 6e  |ble.Error loadin|
00000150  67 20 6f 70 65 72 61 74  69 6e 67 20 73 79 73 74  |g operating syst|
00000160  65 6d 00 4d 69 73 73 69  6e 67 20 6f 70 65 72 61  |em.Missing opera|
00000170  74 69 6e 67 20 73 79 73  74 65 6d 00 00 00 00 00  |ting system.....|
00000180  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001b0  00 00 00 00 00 2c 44 63  9d 08 9e 08 00 00 00 01  |.....,Dc........|
000001c0  01 00 fd fe 3f 3c 3f 00  00 00 be f3 0e 00 00 00  |....?<?.........|
000001d0  01 3d fd fe ff ff fd f3  0e 00 e5 cb 40 0e 00 00  |.=..........@...|
000001e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
00000200  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00008200  20 be 03 00 80 79 07 00  ac 5f 00 00 11 b5 06 00  | ....y..._......|
00008210  01 be 03 00 01 00 00 00  00 00 00 00 00 00 00 00  |................|
00008220  00 20 00 00 00 20 00 00  f8 0f 00 00 31 9a 1d 48  |. ... ......1..H|
00008230  d0 9d 1d 48 01 00 1e 00  53 ef 01 00 01 00 00 00  |...H....S.......|
00008240  00 00 00 00 00 00 00 00  00 00 00 00 01 00 00 00  |................|
00008250  00 00 00 00 0b 00 00 00  80 00 00 00 00 00 00 00  |................|
00008260  02 00 00 00 01 00 00 00  d6 ce 40 e9 33 3a 4d 30  |..........@.3:M0|
00008270  8f 62 60 62 04 e9 34 24  62 6f 6f 74 00 00 00 00  |.b`b..4$boot....|
00008280  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00008600  04 00 00 00 05 00 00 00  06 00 00 00 00 00 e8 0f  |................|
00008610  02 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008620  04 20 00 00 05 20 00 00  06 20 00 00 d2 10 f8 0f  |. ... ... ......|
00008630  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008640  01 40 00 00 02 40 00 00  06 40 00 00 ff 1d f8 0f  |.@...@...@......|
00008650  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008660  04 60 00 00 05 60 00 00  06 60 00 00 fc 1d f6 0f  |.`...`...`......|
00008670  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008680  01 80 00 00 02 80 00 00  06 80 00 00 69 10 f8 0f  |............i...|
00008690  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000086a0  04 a0 00 00 05 a0 00 00  06 a0 00 00 4b 0b f8 0f  |............K...|
000086b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000086c0  01 c0 00 00 02 c0 00 00  06 c0 00 00 ff 1d f8 0f  |................|
000086d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000086e0  04 e0 00 00 05 e0 00 00  06 e0 00 00 fc 1d f8 0f  |................|
000086f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008700  01 00 01 00 02 00 01 00  06 00 01 00 ff 1d f8 0f  |................|
00008710  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008720  04 20 01 00 05 20 01 00  06 20 01 00 fc 1d f8 0f  |. ... ... ......|
00008730  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008740  01 40 01 00 02 40 01 00  06 40 01 00 ff 1d f8 0f  |.@...@...@......|
00008750  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008760  01 60 01 00 02 60 01 00  06 60 01 00 ff 1d f8 0f  |.`...`...`......|
00008770  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008780  01 80 01 00 02 80 01 00  06 80 01 00 ff 1d f8 0f  |................|
00008790  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000087a0  01 a0 01 00 02 a0 01 00  06 a0 01 00 ff 1d f8 0f  |................|
000087b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000087c0  01 c0 01 00 02 c0 01 00  06 c0 01 00 ff 1d f8 0f  |................|
000087d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000087e0  01 e0 01 00 02 e0 01 00  06 e0 01 00 ff 1d f8 0f  |................|
000087f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008800  01 00 02 00 02 00 02 00  06 00 02 00 ff 1d f8 0f  |................|
00008810  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008820  01 20 02 00 02 20 02 00  06 20 02 00 ff 1d f8 0f  |. ... ... ......|
00008830  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008840  01 40 02 00 02 40 02 00  06 40 02 00 ff 1d f8 0f  |.@...@...@......|
00008850  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008860  01 60 02 00 02 60 02 00  06 60 02 00 ff 1d f8 0f  |.`...`...`......|
00008870  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008880  01 80 02 00 02 80 02 00  06 80 02 00 ff 1d f8 0f  |................|
00008890  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000088a0  01 a0 02 00 02 a0 02 00  06 a0 02 00 ff 1d f8 0f  |................|
000088b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000088c0  01 c0 02 00 02 c0 02 00  06 c0 02 00 ff 1d f8 0f  |................|
000088d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000088e0  01 e0 02 00 02 e0 02 00  06 e0 02 00 ff 1d f8 0f  |................|
000088f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008900  01 00 03 00 02 00 03 00  06 00 03 00 ff 1d f8 0f  |................|
00008910  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008920  04 20 03 00 05 20 03 00  06 20 03 00 fc 1d f8 0f  |. ... ... ......|
00008930  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008940  01 40 03 00 02 40 03 00  06 40 03 00 55 1d eb 0f  |.@...@...@..U...|
00008950  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008960  04 60 03 00 05 60 03 00  06 60 03 00 fc 1d f8 0f  |.`...`...`......|
00008970  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008980  01 80 03 00 02 80 03 00  06 80 03 00 ff 1d f8 0f  |................|
00008990  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000089a0  01 a0 03 00 02 a0 03 00  06 a0 03 00 ff 1d f8 0f  |................|
000089b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000089c0  01 c0 03 00 02 c0 03 00  06 c0 03 00 ff 1d f8 0f  |................|
000089d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000089e0  01 e0 03 00 02 e0 03 00  06 e0 03 00 ff 1d f8 0f  |................|
000089f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008a00  01 00 04 00 02 00 04 00  06 00 04 00 ff 1d f8 0f  |................|
00008a10  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008a20  01 20 04 00 02 20 04 00  06 20 04 00 ff 1d f8 0f  |. ... ... ......|
00008a30  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008a40  01 40 04 00 02 40 04 00  06 40 04 00 ff 1d f8 0f  |.@...@...@......|
00008a50  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008a60  01 60 04 00 02 60 04 00  06 60 04 00 ff 1d f8 0f  |.`...`...`......|
00008a70  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008a80  01 80 04 00 02 80 04 00  06 80 04 00 ff 1d f8 0f  |................|
00008a90  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008aa0  01 a0 04 00 02 a0 04 00  06 a0 04 00 ff 1d f8 0f  |................|
00008ab0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008ac0  01 c0 04 00 02 c0 04 00  06 c0 04 00 ff 1d f8 0f  |................|
00008ad0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008ae0  01 e0 04 00 02 e0 04 00  06 e0 04 00 ff 1d f8 0f  |................|
00008af0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008b00  01 00 05 00 02 00 05 00  06 00 05 00 ff 1d f8 0f  |................|
00008b10  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008b20  01 20 05 00 02 20 05 00  06 20 05 00 ff 1d f8 0f  |. ... ... ......|
00008b30  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008b40  01 40 05 00 02 40 05 00  06 40 05 00 ff 1d f8 0f  |.@...@...@......|
00008b50  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008b60  01 60 05 00 02 60 05 00  06 60 05 00 ff 1d f8 0f  |.`...`...`......|
00008b70  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008b80  01 80 05 00 02 80 05 00  06 80 05 00 ff 1d f8 0f  |................|
00008b90  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008ba0  01 a0 05 00 02 a0 05 00  06 a0 05 00 ff 1d f8 0f  |................|
00008bb0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008bc0  01 c0 05 00 02 c0 05 00  06 c0 05 00 ff 1d f8 0f  |................|
00008bd0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008be0  01 e0 05 00 02 e0 05 00  06 e0 05 00 ff 1d f8 0f  |................|
00008bf0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008c00  01 00 06 00 02 00 06 00  06 00 06 00 ff 1d f8 0f  |................|
00008c10  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008c20  04 20 06 00 05 20 06 00  06 20 06 00 fc 1d f8 0f  |. ... ... ......|
00008c30  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008c40  01 40 06 00 02 40 06 00  06 40 06 00 ff 1d f8 0f  |.@...@...@......|
00008c50  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008c60  01 60 06 00 02 60 06 00  06 60 06 00 ff 1d f8 0f  |.`...`...`......|
00008c70  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008c80  01 80 06 00 02 80 06 00  06 80 06 00 ff 1d f8 0f  |................|
00008c90  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008ca0  01 a0 06 00 02 a0 06 00  06 a0 06 00 ff 1d f8 0f  |................|
00008cb0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008cc0  01 c0 06 00 02 c0 06 00  06 c0 06 00 ff 1d f8 0f  |................|
00008cd0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008ce0  01 e0 06 00 02 e0 06 00  06 e0 06 00 ff 1d f8 0f  |................|
00008cf0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008d00  01 00 07 00 02 00 07 00  06 00 07 00 ff 1d f8 0f  |................|
00008d10  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008d20  01 20 07 00 02 20 07 00  06 20 07 00 ff 1d f8 0f  |. ... ... ......|
00008d30  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008d40  01 40 07 00 02 40 07 00  06 40 07 00 ff 1d f8 0f  |.@...@...@......|
00008d50  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008d60  01 60 07 00 02 60 07 00  06 60 07 00 7e 17 f8 0f  |.`...`...`..~...|
00008d70  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008d80  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
*
00009200  ff ff 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00009210  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00009680  ed 41 00 00 00 04 00 00  f7 42 04 48 a9 9d 1d 48  |.A.......B.H...H|
00009690  a9 9d 1d 48 00 00 00 00  00 00 04 00 02 00 00 00  |...H............|
000096a0  00 00 00 00 00 00 00 00  05 02 00 00 00 00 00 00  |................|
000096b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00009b00  ed 41 00 00 00 30 00 00  12 9a 1d 48 12 9a 1d 48  |.A...0.....H...H|
00009b10  12 9a 1d 48 00 00 00 00  00 00 02 00 18 00 00 00  |...H............|
00009b20  00 00 00 00 00 00 00 00  06 02 00 00 07 02 00 00  |................|
00009b30  08 02 00 00 09 02 00 00  0a 02 00 00 0b 02 00 00  |................|
00009b40  0c 02 00 00 0d 02 00 00  0e 02 00 00 0f 02 00 00  |................|
00009b50  10 02 00 00 11 02 00 00  00 00 00 00 00 00 00 00  |................|
00009b60  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00009b80  a4 81 00 00 78 0e 1d 00  ab 9a 1d 48 ab 9a 1d 48  |....x......H...H|
00009b90  95 45 fe 47 00 00 00 00  00 00 01 00 9a 0e 00 00  |.E.G............|
00009ba0  00 00 00 00 00 00 00 00  12 02 00 00 13 02 00 00  |................|
00009bb0  14 02 00 00 15 02 00 00  16 02 00 00 17 02 00 00  |................|
00009bc0  18 02 00 00 19 02 00 00  1a 02 00 00 1b 02 00 00  |................|
00009bd0  1c 02 00 00 1d 02 00 00  1e 02 00 00 1f 03 00 00  |................|
00009be0  00 00 00 00 d9 e9 41 20  00 00 00 00 00 00 00 00  |......A ........|
00009bf0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00009c00  a4 81 00 00 5c 38 01 00  ab 9a 1d 48 ab 9a 1d 48  |....\8.....H...H|
00009c10  95 45 fe 47 00 00 00 00  00 00 01 00 a0 00 00 00  |.E.G............|
00009c20  00 00 00 00 00 00 00 00  5f 09 00 00 60 09 00 00  |........_...`...|
128+0 records in
128+0 records out
65536 bytes (66 kB) copied, 0.0243211 s, 2.7 MB/s
00009c30  61 09 00 00 62 09 00 00  63 09 00 00 64 09 00 00  |a...b...c...d...|
00009c40  65 09 00 00 66 09 00 00  67 09 00 00 68 09 00 00  |e...f...g...h...|
00009c50  69 09 00 00 6a 09 00 00  6b 09 00 00 00 00 00 00  |i...j...k.......|
00009c60  00 00 00 00 da e9 41 20  00 00 00 00 00 00 00 00  |......A ........|
00009c70  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00009c80  a4 81 00 00 cf 72 06 00  ab 9a 1d 48 ab 9a 1d 48  |.....r.....H...H|
00009c90  95 45 fe 47 00 00 00 00  00 00 01 00 40 03 00 00  |.E.G........@...|
00009ca0  00 00 00 00 00 00 00 00  af 09 00 00 b0 09 00 00  |................|
00009cb0  b1 09 00 00 b2 09 00 00  b3 09 00 00 b4 09 00 00  |................|
00009cc0  b5 09 00 00 b6 09 00 00  b7 09 00 00 b8 09 00 00  |................|
00009cd0  b9 09 00 00 ba 09 00 00  bb 09 00 00 bc 0a 00 00  |................|
00009ce0  00 00 00 00 db e9 41 20  00 00 00 00 00 00 00 00  |......A ........|
00009cf0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00009d00  a4 81 00 00 34 bb 0d 00  ab 9a 1d 48 ab 9a 1d 48  |....4......H...H|
00009d10  95 45 fe 47 00 00 00 00  00 00 01 00 e8 06 00 00  |.E.G............|
00009d20  00 00 00 00 00 00 00 00  4f 0b 00 00 50 0b 00 00  |........O...P...|
00009d30  51 0b 00 00 52 0b 00 00  53 0b 00 00 54 0b 00 00  |Q...R...S...T...|
00009d40  55 0b 00 00 56 0b 00 00  57 0b 00 00 58 0b 00 00  |U...V...W...X...|
00009d50  59 0b 00 00 5a 0b 00 00  5b 0b 00 00 5c 0c 00 00  |Y...Z...[...\...|
00009d60  00 00 00 00 dc e9 41 20  00 00 00 00 00 00 00 00  |......A ........|
00009d70  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00009d80  a4 81 00 00 6b 1f 79 00  b5 9a 1d 48 c8 9a 1d 48  |....k.y....H...H|
00009d90  be 9a 1d 48 00 00 00 00  00 00 01 00 d0 3c 00 00  |...H.........<..|
00009da0  00 00 00 00 00 00 00 00  c3 0e 00 00 c4 0e 00 00  |................|
00009db0  c5 0e 00 00 c6 0e 00 00  c7 0e 00 00 c8 0e 00 00  |................|
00009dc0  c9 0e 00 00 ca 0e 00 00  cb 0e 00 00 cc 0e 00 00  |................|
00009dd0  cd 0e 00 00 ce 0e 00 00  cf 0e 00 00 d0 0f 00 00  |................|
00009de0  00 00 00 00 dd e9 41 20  00 00 00 00 00 00 00 00  |......A ........|
00009df0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00010000
cypr3ss@server1:~$ 

This volume isn't now, and has never been (as far as i can remember) a boot 
volume.

I also did some more googling and found this, which (afaict) is just a 
replication of the above, but thought it may help.

$ sudo hexdump -C /dev/sdc | head
00000000  33 c0 8e d0 bc 00 7c fb  50 07 50 1f fc be 1b 7c  |3.....|.P.P....||
00000010  bf 1b 06 50 57 b9 e5 01  f3 a4 cb bd be 07 b1 04  |...PW...........|
00000020  38 6e 00 7c 09 75 13 83  c5 10 e2 f4 cd 18 8b f5  |8n.|.u..........|
00000030  83 c6 10 49 74 19 38 2c  74 f6 a0 b5 07 b4 07 8b  |...It.8,t.......|
00000040  f0 ac 3c 00 74 fc bb 07  00 b4 0e cd 10 eb f2 88  |..<.t...........|
00000050  4e 10 e8 46 00 73 2a fe  46 10 80 7e 04 0b 74 0b  |N..F.s*.F..~..t.|
00000060  80 7e 04 0c 74 05 a0 b6  07 75 d2 80 46 02 06 83  |.~..t....u..F...|
00000070  46 08 06 83 56 0a 00 e8  21 00 73 05 a0 b6 07 eb  |F...V...!.s.....|
00000080  bc 81 3e fe 7d 55 aa 74  0b 80 7e 10 00 74 c8 a0  |..>.}U.t..~..t..|
00000090  b7 07 eb a9 8b fc 1e 57  8b f5 cb bf 05 00 8a 56  |.......W.......V|

I don't know what this output should look like when it's "correct", but I get 
the feeling this isn't right.

Regards,

Stephen.

Stephen Porter wrote:
> Hello,
> 
> Hoping someone may be able to offer some advice/assistance.
> 
> I lost power twice (within a few hours) to my machine which had a ~2.2TB
> XFS volume on it.  The first time the machine (running Xubuntu 8.04)
> came back up ok, the second time the XFS volume will not mount.  Is
> there any chance of recovering the data? /dev/sdc is seen by xubuntu as
> one ~2.2TB disk, and I put the XFS file system straight onto the disk.
> It's 4x750GB drives on a hardware raid controller (rocketraid 2320).
> Driver/module for rocket raid (rr232x) is loaded ok.

hm, not an in-kernel driver, I guess?

> In the system log I see:
> 
> XFS: bad magic number
> 
> XFS: SB validate failed
> 
> I tried running xfs_check, the result of this was:
> 
> xfs_check /dev/sdc
> xfs_check: unexpected XFS SB magic number 0x33c08ed0
> xfs_check: size check failed
> xfs_check: read failed: Invalid argument
> xfs_check: data size check failed
> xfs_check: failed to alloc -225176656 bytes: Cannot allocate memory
> 
> I looked at running xfs_repair, but the man page states that this will
> only work on a volume that has been unmounted cleanly... as I lost power
> the volume has not been unmounted cleanly, but I cannot mount it again
> to unmount it cleanly.

If you have to, you can zero the log w/ xfs_repair as a last resort.

> Running xfs_repair gives the following:
> 
> xfs_repair -n /dev/sdc
> 
> Phase 1 - find and verify superblock...
> 
> bad primary superblock - bad magic number !!!
> 
> ...attempting to find secondary superblock...
> 
> ...found candidate secondary superblock... unable to verify superblock,
> continuing...

I always wished it said where, and why it did not verify....

> (the above appears a few times, until finally)
> 
> ...Sorry, could not find valid secondary superblock
> 
> Exiting now.
> 
> I've seen it mentioned in other posts to the xfs archive to check that
> there is an xfs volume there, so I've also included the output of "dd
> if=/dev/sdc bs=512 count=1 iflag=direct 2> /dev/null | od -Ax -x" below:
> 
> $ dd if=/dev/sdc bs=512 count=1 iflag=direct 2> /dev/null | od -Ax -x
> 
> 000000 c033 d08e 00bc fb7c 0750 1f50 befc 7c1b
> 000010 1bbf 5006 b957 01e5 a4f3 bdcb 07be 04b1


Can you try piping it through "hexdump -C" instead, I'm more used to
eyeballing that output :)

You might also try looking a bit further:

dd if=/dev/sdc bs=512 count=128 iflag=direct | hexdump -C | grep XFSB

to see if maybe the raid card does something else at the front of your
disk and the superblock is further in, and something got scrambled up?
Just a longshot....

-Eric





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