Date: Tue, 25 Oct 2005 10:17:43 +0000 From: aleksandr.derevianko@ru.transport.bombardier.com To: freebsd-questions@freebsd.org Subject: NEC DVD_RW - file read problems. Message-ID: <OFDFD3477A.8ED6A831-ON002570A5.0037038A@UK.BOMBARDIER.TRANSPORT.COM>
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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
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