NEC DVD_RW - file read problems.

aleksandr.derevianko at ru.transport.bombardier.com aleksandr.derevianko at ru.transport.bombardier.com
Mon Oct 24 23:17:47 PDT 2005





Hello All,

I have the following problem:

OS: FreeBSD 4.11-RELEASE.
DVD RW: acd0: DVD-R <_NEC DVD_RW ND-3500AG> at ata1-master UDMA33

I use DVD R's primary for data backup. The backup data is archived and splitted on files ~500Mb size,
which was written on DVD-R's. I have also store the MD5 sums of those files in small checksum file.

The problem is: sometimes then i check content on DVD the checksum is differs. Where is no read errors on console,
and several attempts to calculate checksum return different results.


bash-2.05b# grep 00001 /cdrom/md5.sums
acc8b491f03bfa01e341808773a6f94f depot.147.tar.00001
bash-2.05b# md5 /cdrom/depot.147.tar.00001
MD5 (/cdrom/depot.147.tar.00001) = d821bd902c4b0e9c12510f302c10ee71

# File seems cached in RAM

bash-2.05b# md5 /cdrom/depot.147.tar.00001
MD5 (/cdrom/depot.147.tar.00001) = d821bd902c4b0e9c12510f302c10ee71
bash-2.05b# umount /cdrom

# After unmounting and mounting again - different (correct) checksum.

bash-2.05b# !mou
mount /cdrom
bash-2.05b# md5 /cdrom/depot.147.tar.00001
MD5 (/cdrom/depot.147.tar.00001) = acc8b491f03bfa01e341808773a6f94f

# Now the checksum is OK.

It seems for me that sometimes device correct soft read errors on media, and sometimes - does not.

Does anybody have the same expirience (i.e. checksum differs without read errors) ?


Best Regards,
Alexander Derevyanko



More information about the freebsd-questions mailing list