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Re: DVD-Ram diagnostics



Greetings,

on saturday april 17th 2004 12:12 Andy Polyakov wrote:
> >>>I was told, that DVD-Ram is very secure because of its structure. Today
> >>> a nearly four months old DVD-Ram failed. (Maxell, non-cartrigde
> >>> version). My LG-4081B throw some i/o errors when I tried to dd the
> >>> dvd-ram with random data in order to encrypt it.
> >>>I could not see any scratches, dust or any fingerprints on the dvd.
> >>>What might have gone wrong? How can I detect it? How do I proctect my
> >>>other backups?

> But back to the problem. You've got to elaborate on "some i/o errors."

Ok:
Apr 14 13:00:34 donald kernel: end_request: I/O error, dev 16:00 (hdc), sector 
12028
Apr 14 13:00:34 donald kernel: end_request: I/O error, dev 16:00 (hdc), sector 
12030

etc.

> > Is it a media-error or do I do have to upgrade firmware or are there any
> > known linux-kernel issues?
>
> Quoting specification:
>
> "The DVD-RAM format is designed to enable the following Linear
> Replacement methods, with some consideration for issues of real-time
> data recording, where for example the reassignments are disabled during
> some operations.
>
> - When recording data with verification by the WRITE AND VERIFY (10)
> command, the logical unit has an opportunity to evaluate the written
> data and if the data is found defective, the logical unit may perform a
> Linear Replacement.
>
> - For data recorded without verification, the logical unit has an
> opportunity to evaluate the written data when the host attempts to read
> the data from that LBA and if the data is found defective but
> correctable by ECC, the logical unit may perform the Linear Replacement
> operation, if read reassignment is enabled."
>
> As you read the quote you ask yourself following questions.
>
> - Was data recorded in "real-time mode, where reassignments are
> disabled?" No. "Real-time recording" implies that writes are performed
> with WRITE(12) command with "Streaming" bit set. Linux kernel never uses
> it. - But was data recorded "with verification by the WRITE AND VERIFY (10)
> command?" No. Linux kernel doesn't use WRITE AND VERYFY command when
> writing DVD-RAM.

Can I patch linux for doing so or which (unix-like) os do you recommend for 
doing so?

> - But is "read reassignment enabled?" I don't know. How to tell? There
> is an ARRE, Automatic Read Reallocation Enable bit in page 01. You can
> dump the pages with 'dvd+rw-mediainfo /dev/dvd verbose'. Send the output
> to the list, so we can see if ARRE is on.

Ok, appended . (Note: there is no meaningful data on the dvd. I did dd 
if=/dev/urandom of=/dev/hdc in order to prepare the dvd for crypto-data.)

> However! Even if ARRE is on, 

Puhh... I don't see any entry indicating whether it is or it is not.

> there is yet another possibility for things
> to *appear* broken. Specfication mentions that unit raises a warning
> condition when Supplementary Spare Aread is about to be exhausted and
> needs to be grown. If Linux kernel does not interpret it as warning (at
> the very least it could ignore it and log a message at console), it
> shall appear as I/O error to application. As for growing spare area.
> Note that it implies that filesystem can be shrunk. As it's problematic
> to shrink file systems, it might actually make sense to maximize the
> spare area prior creating file system. Note that I don't know if
> there're Linux apps readily available that will let you grow spare area
> or manipulate ARRE bit. The above suggestions has rather theoretical
> character as they are not based on personal experience (don't have
> DVD-RAM capable unit).

Puh... sounds bad. What do you recommend to get safe backups? (No - Windows is 
not an option ;)

> Bottom line. "some I/O erors" is not good enough to tell what's going
> on. Examine kernel log to find out the exact error code. A.

see above.
Thanks for your help.

Keep smiling
yanosz


dvd+rw-mediainfo /dev/hdc verbose

INQUIRY:                [HL-DT-ST][DVDRAM GSA-4081B][A100]
MODE SENSE[#3Fh]:
 01:    80 13 00 00 00 00 03 00 00 00
 05:    60 05 08 10 00 00 00 00 00 00 00 20 00 96 00 00
        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
        00 00
 88:    04 00 08 00 00 00 00 80 00 80
 8D:    00 0b 00 3c 00 4b
 0E:    04 00 00 00 00 4b 01 ff 02 ff 00 00 00 00
 18:    00 01 00 01 00 00 00 01 00 01 00 01 00 00 00 01
        00 01 00 01 00 01 00 01 00 00
 9A:    00 03 00 00 04 b0 00 00 09 60
 9C:    00 04 00 00 02 58 00 00 00 00
 9D:    00 00 00 00 00 1e 2a 30
 A0:    01 00 00 64 00 03 00 00 00 00
 2A:    3f 37 f1 73 29 23 10 3b 01 00 08 00 10 3b 00 00
        10 3b 10 3b 00 01 00 00 00 00 10 3b 00 01 00 00
        10 3b 00 00 00 00 00 00 00 00 00 00 00 00 00 00
        00 00 00 00 00 00 00 00 00 00 00 00 00 00
MODE SENSE[#2A]:
 2A:    3f 37 f1 73 29 23 10 3b 01 00 08 00 10 3b 00 00
        10 3b 10 3b 00 01 00 00 00 00 10 3b 00 01 00 00
        10 3b 00 00 00 00 00 00 00 00 00 00 00 00 00 00
        00 00 00 00 00 00 00 00 00 00 00 00 00 00
GET [CURRENT] CONFIGURATION:
 0000:  00 12 01 00 00 11 00 00 00 14 00 00 00 13 00 00
        00 1a 00 00 00 1b 00 00 00 10 00 00 00 09 00 00
        00 0a 00 00 00 08 00 00 00 02 01 00
 0001:  00 00 00 02
 0002:  00 00 00 00
 0003:  29 00 00 00
 0004:  02 00 00 00
 0010:  00 00 08 00 00 10 01 00
 001F:
 0020:  00 22 21 1f 00 00 08 00 00 10 01 00
 0023:
 0024:  80 00 00 00
 0037:  00 07 00 00
 0100:
 0101:  01 00 00 00
 0105:
 0107:  1f 00 00 00
 0108:  4b 31 45 33 43 32 42 34 30 35 35 20
 010B:  00 00 00 01
 010C:  32 30 30 33 31 31 32 38 31 32 33 34 35 36 00 00
 Mounted Media:         12h, DVD-RAM
:-[ READ DVD STRUCTURE#11 failed with SK=5h/ASC=24h/ACQ=00h]: Input/output 
error
 Current Write Speed:   3.0x1385=4155KB/s
 Write Speed #0:        3.0x1385=4155KB/s
GET CURRENT PERFORMANCE:        02 00 00 00 00 00 00 00 00 00 10 3b 00 22 21 
1f 00 00 10 3b
 Write Performance:     3.0x1385=4155KB/s@[0 -> 2236703]
GET PERFORMANCE:        02 00 00 00 00 22 21 1f 00 00 10 3b 00 00 10 3b
 Speed Descriptor#0:    02/2236703 R@3.0x1385=4155KB/s W@3.0x1385=4155KB/s
READ DVD STRUCTURE[#FF]:
 STRUCTURE#00           40:2052
 STRUCTURE#01           40:8
 STRUCTURE#02           40:2052
 STRUCTURE#03           40:192
 STRUCTURE#04           c0:2052
 STRUCTURE#05           40:8
 STRUCTURE#06           40:24
 STRUCTURE#07           40:24580
 STRUCTURE#08           40:2052
 STRUCTURE#09           40:8
 STRUCTURE#0a           40:16
 STRUCTURE#0b           40:8
 STRUCTURE#c0           c0:8
READ DVD STRUCTURE[#0h]:        16 0f 04 42 00 03 10 00 00 26 5f 5f 00 00 00 
00
 Media Book Type:       16h, DVD-RAM book [revision 6]
 Legacy lead-out at:    2314080*2KB=4739235840
READ DISC INFORMATION:  00 20 1f 01 01 01 01 00 ff 00 00 00 00 00 00 00
 Disc status:           other
 Number of Sessions:    1
 State of Last Session: complete
 "Next" Track:          1
 Number of Tracks:      1
READ FORMAT CAPACITIES:
 formatted:             2236704*2048=4580769792
 00h(800):              2236704*2048=4580769792
 00h(800):              2295072*2048=4700307456
 01h(800):              2226976*2048=4560846848
 01h(800):              2217248*2048=4540923904
READ TRACK INFORMATION[#1]:     00 22 01 01 00 04 01 00 00 00 00 00 00 00 00 
00
 Track State:           complete
 Track Start Address:   0*2KB
 Free Blocks:           0*2KB
 Track Size:            2236704*2KB
FABRICATED TOC:         18 1 1
 Track#1  :             14@0
 Track#AA :             14@2236704
 Multi-session Info:    #1@0



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