[colug-432] Problem for January Meeting

[jep200404 at columbus.rr.com]

On Tue, 12 Jan 2016 09:12:19 -0500, Scott Merrill <skippy at skippy.net> wrote:

> As always, feel free to bring with you any ailing or problematic systems
> for expert diagnosis (or destruction).

I hope to get some help explaining why dd is having trouble 
writing to an SDHC module. I hope to have the SDHC module 
and USB adapter at tonight's meeting.

There was initial apparent success at amazing speed,
but reads revealed that it was not actually writing all the zeros.
 For example: 

    [root at main flash]# date;time dd if=/dev/zero bs=1M seek=2272 of=/dev/sdb;date
    Sun Dec 20 14:26:17 EST 2015 
    dd: error writing ‘/dev/sdb’: No space left on device
    12922+0 records in
    12921+0 records out
    13549174784 bytes (14 GB) copied, 110.059 s, 123 MB/s

    real    1m50.061s
    user    0m0.007s
    sys     0m9.680s
    Sun Dec 20 14:28:07 EST 2015
    [root at main flash]# date;dd if=/dev/sdb bs=1M | od | head;date
    Sun Dec 20 14:28:33 EST 2015
    0000000 000000 000000 000000 000000 000000 000000 000000 000000
    *
    22600000000 122700 000001 113400 000006 052131 000000 055000 000006
    22600000020 122665 000001 000000 000000 000002 000000 000002 000000
    22600000040 100000 000000 100000 000000 017040 000000 000000 000000
    22600000060 000211 000000 000000 177777 167523 000000 000001 000000
    22600000100 000211 000000 000000 000000 000000 000000 000001 000000
    22600000120 000000 000000 000013 000000 000400 000007 000074 000000
    22600000140 001102 000000 000173 000000 005753 000232 024034 066504
    22600000160 034611 142347 015435 130705 000000 000000 000000 000000
    Sun Dec 20 14:31:25 EST 2015
    [root at main flash]# date;time dd if=/dev/zero bs=1M seek=2272 count=12000 of=/dev/sdb;date

Later I got errors, which I considered to be progress.
dd would eventually crash. I would use the number of 
records reported to determine where to resume writing 
with the seek parameter.

    [root at main flash]# date;time dd if=/dev/zero bs=512 seek=17194872 of=/dev/sdb;date
    Tue Dec 29 09:52:33 EST 2015
    dd: error writing ‘/dev/sdb’: Input/output error
    469985+0 records in
    469984+0 records out
    240631808 bytes (241 MB) copied, 53.4608 s, 4.5 MB/s

    real    0m53.463s
    user    0m0.086s
    sys     0m1.562s
    Tue Dec 29 09:53:26 EST 2015
    [root at main flash]# python
    Python 2.7.5 (default, Jun 24 2015, 00:41:19)
    [GCC 4.8.3 20140911 (Red Hat 4.8.3-9)] on linux2
    Type "help", "copyright", "credits" or "license" for more information.
    >>> 17194872+469984
    17664856
    >>>
    [root at main flash]# date;time dd if=/dev/zero bs=512 seek=17664856 of=/dev/sdb;date
    Tue Dec 29 10:02:52 EST 2015
    dd: error writing ‘/dev/sdb’: Input/output error
    107377+0 records in
    107376+0 records out
    54976512 bytes (55 MB) copied, 13.4267 s, 4.1 MB/s

    real    0m13.428s
    user    0m0.040s
    sys     0m0.337s
    Tue Dec 29 10:03:06 EST 2015
    [root at main flash]# expr 17664856 + 107376
    17772232
    [root at main flash]# date;time dd if=/dev/zero bs=512 seek=17772232 of=/dev/sdb;date

dmesg revealed things like:

    [1605029.263795] sd 17:0:0:0: [sdb]
    [1605029.263801] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
    [1605029.263803] sd 17:0:0:0: [sdb]
    [1605029.263806] Sense Key : Not Ready [current]
    [1605029.263809] Info fld=0x0
    [1605029.263812] sd 17:0:0:0: [sdb]
    [1605029.263816] <<vendor>> ASC=0xff ASCQ=0xffASC=0xff <<vendor>> ASCQ=0xff
    [1605029.263820] sd 17:0:0:0: [sdb] CDB:
    [1605029.263821] Write(10): 2a 00 01 22 ac 20 00 00 f0 00
    [1605029.263829] end_request: I/O error, dev sdb, sector 19049504
    [1605029.263833] quiet_error: 80 callbacks suppressed
    [1605029.263835] Buffer I/O error on device sdb, logical block 2381188
    [1605029.263837] lost page write due to I/O error on sdb
    [1605029.263840] Buffer I/O error on device sdb, logical block 2381189
    [1605029.263842] lost page write due to I/O error on sdb
    [1605029.263845] Buffer I/O error on device sdb, logical block 2381190
    [1605029.263846] lost page write due to I/O error on sdb
    [1605029.263849] Buffer I/O error on device sdb, logical block 2381191
    [1605029.263851] lost page write due to I/O error on sdb
    [1605029.263853] Buffer I/O error on device sdb, logical block 2381192
    [1605029.263855] lost page write due to I/O error on sdb
    [1605029.263858] Buffer I/O error on device sdb, logical block 2381193
    [1605029.263859] lost page write due to I/O error on sdb
    [1605029.263862] Buffer I/O error on device sdb, logical block 2381194
    [1605029.263864] lost page write due to I/O error on sdb
    [1605029.263866] Buffer I/O error on device sdb, logical block 2381195
    [1605029.263868] lost page write due to I/O error on sdb
    [1605029.263870] Buffer I/O error on device sdb, logical block 2381196
    [1605029.263872] lost page write due to I/O error on sdb
    [1605029.263874] Buffer I/O error on device sdb, logical block 2381197
    [1605029.263876] lost page write due to I/O error on sdb