Silent errors when reading CDs

[Dmitry Morozovsky]

Hi there,

On Sat, 10 Jul 2004, Jean-Sebastien Roy wrote:

JR> I'm currently using FreeBSD 4.10 on an HP D530 SFF.
JR> The system is perfectly stable except for the following problem
JR> I'm unable to understand :
JR>
JR> When I mount a cdrom (mount /cdrom), then calculate the MD5 hash
JR> of a big file on a CD (md5 /cdrom/bigfile), the results are often random:
JR> unmounting, mounting again and calculating again the MD5 often result in
JR> a different value. What disturb me the most is that absolutely no errors
JR> are reported in any log (no read errors for example).
JR>
JR> I thought the CDROM reader, a LITE-ON LTR-48327S PQS3, was the culprit,
JR> so I replaced it with a PLEXTOR DVDR PX-712A and got the exact same
JR> results (i.e. random MD5 values). I checked the RAM using memtest and
JR> got no errors. The problem does not occur for files on the harddisk.
JR>
JR> hw.ata.atapi_dma is set since both drives support it and it seems to be
JR> required for proper CD/DVD burning. The CD drive is the master on its
JR> own ATA bus.
JR>
JR> While the problem occurs on multiple CDs (mostly RW), to my surprise, I
JR> was not able to reproduce the problem by reading big files on DVDs.
JR>
JR> Could someone provide me a hint on what to check next or how to fix this
JR> problem ? Can errors on CDs generate such a behavior ?

What if you copy that big file from CD to HD twice (possibly with
unmounting/remounting in the middle) and check MD5s there?

Testing your memory with memtest86.com's test would also be helpful to
eliminate RAM issues.

Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck at rinet.ru ***
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