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Reading "raw" disk greater than 1 terabyte


Hello all,
I have not been able to find anything in cygwin implying that the read()
function call or 'dd' can read a "raw" disk pass the 1 terabyte limit.
I get similar result as 'dd' when using the read() function call; the
lseek()function call appears to work fine SEEK_SET beyond 1 terabyte
limit.  Is this a known behavior?

Thank you so much for your time and effort.

Joe Loh

I started experimenting with 'dd' and observed the following with a
"raw" 1.5 terabyte disk running CYGWIN_NT-5.1 1.5.13(0.122/4/2)
2005-03-01 11:01 under Windows Server 2003 (Enterprise Edition):

Output from /proc/partitions:
major minor  #blocks  name

    8     0  39070080 sda
    8     1     40131 sda1
    8     2  39021885 sda2
    8    16 1610612640 sdb
    8    17 1610604576 sdb1

Output from dd:
$ dd if=\\\\.\\physicaldrive1 ibs=1024 skip=1610612600 count=10 | od -x
dd: reading `\\\\.\\physicaldrive1': Is a directory
0+0 records in
0+0 records out
0000000

Same command but using /dev/sdb instead:
$ dd if=/dev/sdb ibs=1024 skip=1610612600 count=10 | od -x
dd: reading `/dev/sdb': Invalid request code
0+0 records in
0+0 records out
0000000

Repeat at the 1 terabyte mark:
$ dd if=\\\\.\\physicaldrive1 ibs=1024 skip=1073741824 count=10 | od -x
-w32
dd: reading `\\\\.\\physicaldrive1': Is a directory
0+0 records in
0+0 records out
0000000

Same as above but with /dev/sdb:
$ dd if=/dev/sdb ibs=1024 skip=1073741824 count=10 | od -x -w32
dd: reading `/dev/sdb': Invalid request code
0+0 records in
0+0 records out
0000000

Now start 1 block below the 1 terabyte mark:
$ dd if=\\\\.\\physicaldrive1 ibs=1024 skip=1073741823 count=10 | od -x
-w32
0000000 0c7a 1b48 2b94 172b 0d6e 133a ba9e 4847 0024 5d2d 6b46 3564 dc0c
53be c2c8 1760
0000040 e475 5193 e72a 447b 9986 2285 3e1e 7122 5d98 7f1c e75a 1f44 d5bf
64b0 223e 15a1
0000100 1f8a 05cf a000 611f 91d0 6341 2198 65cc b65e 3cb1 f473 373b c659
412d 1e7d 2439
0000140 b31f 2200 c9a9 5bef a566 5ba0 fa89 0fca 4078 5706 b2ea 5b72 4f8d
4740 d686 4f26
0000200 2002 7ece a458 0e97 94e4 05a6 07a1 7b79 1a5b 46e4 70b9 297e 96f7
2c1a 48c0 05ad
0000240 3829 3383 262a 6bdc c6b8 424d 7c0a 0031 749f 30c6 8bbd 3512 4083
5494 83d6 5117
0000300 8031 5ed0 4198 4a90 8866 44c2 03ce 3f89 e9f8 3c58 b7bb 7168 9028
11f6 3b4e 5272
dd: reading `\\\\.\\physicaldrive1': Is a directory
1+0 records in
2+0 records out
0000340 a82b 4993 c4c9 7d05 a83f 05ba c309 217b 950b 4441 282f 2da0 3d0f
6dae dc0a 4a2a
0000400 3a90 43d4 e6ba 2250 ceef 6d5b e500 266e 76b6 3a7c c4b9 4155 6f31
65e6 2e3a 7b8e
0000440 2135 337d 38fb 5c0f 15f4 6b66 7d41 7b2b 7593 642c 3946 22db 348a
668d 849f 4074
0000500 03c8 21af 50be 6921 1fde 0a3c 2d11 7150 f135 46be f2dc 21cd 5ada
5803 cb5a 4441
0000540 a4b8 3b8d 4a93 5039 220a 614f f06f 1243 10c7 2a5e 8e8c 059f 8c36
2e47 44f6 5b46
0000600 a14a 6259 33b7 6a6c 69f6 65b7 c9a5 6c8d a750 50b1 9e93 3f5f e566
1ea3 9b41 1a29
0000640 d5d2 218f df34 6a1e 055a 10d0 6055 490f 91ec 107d 2569 23f7 22f1
36b9 1848 34a5
0000700 39f8 42dd eb13 4a08 525e 0f81 a145 7346 f423 2205 3748 34df 7316
2aa6 bf3a 15cd
0000740 8404 76c5 5f87 215e a92e 3ad1 292d 1aba 5710 33e5 f60e 15b6 1c45
1ed4 05d2 778c
0001000 4e21 1b48 6685 2801 ba47 73f1 c6c9 02fc b7a7 215e 460e 516b 6ae4
59c4 ccc6 6e45
0001040 13b9 2887 eb78 3c1f 321e 539c 7a74 339e 7025 6979 c33c 23b1 aa72
6b88 5985 596e
0001100 58a1 5bb7 e111 621b 5569 1455 6aec 6e5a e48d 7221 1f85 0f24 5c87
0c91 a983 1b51
0001140 e578 0e4f 309f 1f62 26d1 6766 985f 637e b801 0c45 4ff2 3533 b427
3bc5 8b19 30b6
0001200 2f4b 2066 f58b 14aa 8346 63de 9be3 257c 674f 17de 7fc7 0a50 e71b
2af4 b3a5 3470
0001240 3088 5322 5b5b 69a0 e98a 1ecd 72d2 609f 6a8d 042b 511e 3e60 a890
256d 9922 4255
0001300 a934 01b8 95ce 026c 08a0 26df 544f 7caf 4e7c 5ac8 dd74 1498 f53c
3ff2 56f0 67c2
0001340 dbc8 07d9 2b7e 6fec 9699 7a1b 5570 293c 4136 380d 5cf9 6e34 17f5
2fc4 ee52 7300
0001400 847a 421e 877f 618b d4e1 0f6c 07b0 320c cd7b 33cc 60ce 4ac6 9abc
25fd c020 2cb9
0001440 8bd0 56f4 3149 5107 d92e 2f34 7338 369e 7d8b 5c9e 602e 2944 812c
4806 94a5 230a
0001500 ee9c 0ba4 49bc 792d 13cb 0c44 7ab7 496f aa0b 35e1 d3cf 7262 f5b4
363f 183f 211c
0001540 e114 3b7b 068e 41f6 7676 7f28 7e32 3979 2218 574c 826e 4752 2856
79f1 64a5 478f
0001600 b157 1718 d299 5622 66fd 0830 703e 21b9 07be 1578 55f4 7b44 4565
4367 0c75 30fd
0001640 ee73 353c db53 334a 4073 7785 7b52 4d4a 6c22 54e6 57b9 63c5 65db
3102 2600 146d
0001700 d47a 09d9 9aa3 3c0c 6221 5f7c 9580 5f0e 3741 3679 a857 501a 10d7
0622 9666 267f
0001740 1649 026b 13dc 4484 f3a8 3b33 b8f5 4fc1 05bb 3756 545e 7092 210f
16e1 6b85 1641
0002000

Same as above starting 1 block below the 1 terabyte mark but using
/dev/sdb:
$ dd if=/dev/sdb ibs=1024 skip=1073741823 count=10 | od -x -w32
10+0 records in
20+0 records out
0000000 0c7a 1b48 2b94 172b 0d6e 133a ba9e 4847 0024 5d2d 6b46 3564 dc0c
53be c2c8 1760
0000040 e475 5193 e72a 447b 9986 2285 3e1e 7122 5d98 7f1c e75a 1f44 d5bf
64b0 223e 15a1
0000100 1f8a 05cf a000 611f 91d0 6341 2198 65cc b65e 3cb1 f473 373b c659
412d 1e7d 2439
0000140 b31f 2200 c9a9 5bef a566 5ba0 fa89 0fca 4078 5706 b2ea 5b72 4f8d
4740 d686 4f26
0000200 2002 7ece a458 0e97 94e4 05a6 07a1 7b79 1a5b 46e4 70b9 297e 96f7
2c1a 48c0 05ad
0000240 3829 3383 262a 6bdc c6b8 424d 7c0a 0031 749f 30c6 8bbd 3512 4083
5494 83d6 5117
0000300 8031 5ed0 4198 4a90 8866 44c2 03ce 3f89 e9f8 3c58 b7bb 7168 9028
11f6 3b4e 5272
0000340 a82b 4993 c4c9 7d05 a83f 05ba c309 217b 950b 4441 282f 2da0 3d0f
6dae dc0a 4a2a
0000400 3a90 43d4 e6ba 2250 ceef 6d5b e500 266e 76b6 3a7c c4b9 4155 6f31
65e6 2e3a 7b8e
0000440 2135 337d 38fb 5c0f 15f4 6b66 7d41 7b2b 7593 642c 3946 22db 348a
668d 849f 4074
0000500 03c8 21af 50be 6921 1fde 0a3c 2d11 7150 f135 46be f2dc 21cd 5ada
5803 cb5a 4441
0000540 a4b8 3b8d 4a93 5039 220a 614f f06f 1243 10c7 2a5e 8e8c 059f 8c36
2e47 44f6 5b46
0000600 a14a 6259 33b7 6a6c 69f6 65b7 c9a5 6c8d a750 50b1 9e93 3f5f e566
1ea3 9b41 1a29
0000640 d5d2 218f df34 6a1e 055a 10d0 6055 490f 91ec 107d 2569 23f7 22f1
36b9 1848 34a5
0000700 39f8 42dd eb13 4a08 525e 0f81 a145 7346 f423 2205 3748 34df 7316
2aa6 bf3a 15cd
0000740 8404 76c5 5f87 215e a92e 3ad1 292d 1aba 5710 33e5 f60e 15b6 1c45
1ed4 05d2 778c
0001000 4e21 1b48 6685 2801 ba47 73f1 c6c9 02fc b7a7 215e 460e 516b 6ae4
59c4 ccc6 6e45
0001040 13b9 2887 eb78 3c1f 321e 539c 7a74 339e 7025 6979 c33c 23b1 aa72
6b88 5985 596e
0001100 58a1 5bb7 e111 621b 5569 1455 6aec 6e5a e48d 7221 1f85 0f24 5c87
0c91 a983 1b51
0001140 e578 0e4f 309f 1f62 26d1 6766 985f 637e b801 0c45 4ff2 3533 b427
3bc5 8b19 30b6
0001200 2f4b 2066 f58b 14aa 8346 63de 9be3 257c 674f 17de 7fc7 0a50 e71b
2af4 b3a5 3470
0001240 3088 5322 5b5b 69a0 e98a 1ecd 72d2 609f 6a8d 042b 511e 3e60 a890
256d 9922 4255
0001300 a934 01b8 95ce 026c 08a0 26df 544f 7caf 4e7c 5ac8 dd74 1498 f53c
3ff2 56f0 67c2
0001340 dbc8 07d9 2b7e 6fec 9699 7a1b 5570 293c 4136 380d 5cf9 6e34 17f5
2fc4 ee52 7300
0001400 847a 421e 877f 618b d4e1 0f6c 07b0 320c cd7b 33cc 60ce 4ac6 9abc
25fd c020 2cb9
0001440 8bd0 56f4 3149 5107 d92e 2f34 7338 369e 7d8b 5c9e 602e 2944 812c
4806 94a5 230a
0001500 ee9c 0ba4 49bc 792d 13cb 0c44 7ab7 496f aa0b 35e1 d3cf 7262 f5b4
363f 183f 211c
0001540 e114 3b7b 068e 41f6 7676 7f28 7e32 3979 2218 574c 826e 4752 2856
79f1 64a5 478f
0001600 b157 1718 d299 5622 66fd 0830 703e 21b9 07be 1578 55f4 7b44 4565
4367 0c75 30fd
0001640 ee73 353c db53 334a 4073 7785 7b52 4d4a 6c22 54e6 57b9 63c5 65db
3102 2600 146d
0001700 d47a 09d9 9aa3 3c0c 6221 5f7c 9580 5f0e 3741 3679 a857 501a 10d7
0622 9666 267f
0001740 1649 026b 13dc 4484 f3a8 3b33 b8f5 4fc1 05bb 3756 545e 7092 210f
16e1 6b85 1641
0002000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0000 0000 0000
*
0024000


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