Hi, > # growisofs -dvd-compat -speed=1 -Z /dev/hdc=myDVD.iso > # dd if=/dev/hdc bs=2048 count=2002922 | md5sum > dd: reading `/dev/hdc': Input/output error > 1938744+0 records in > > 1) Is this the dreaded readahead bug again?
I doubt it strongly. 2002922-1938744 = 64178 blocks missing That's 125 MB. No readahead does 125 MB. The hard "read-ahead" bug is with CD which have been burned in TAO mode. This mode appends 2 sectors which cannot be read via the SCSI SPC command READ but only via SCSI MMC command READ CD (if ever, i did not try yet). These sectors are nevertheless counted in the TOC info of CD media as part of the track. One cannot easily determine whether they are readable or not - unless one tries. Our dear kernels seem to get confused by the inability to read these announced sectors. The answer was to attach some blocks as sacrifice to this bug-or-feature. The safe size for padding once used to be 32 kB. At some time it grew and an urban legend emerged that 150 sectors (= 2 seconds of music) might be the new limit. Well, 300 kB seems to be safe, indeed ... up to now. Cargo cult. There is no confirmed sighting of readahead bugs on DVD. We got lots of others. Maybe they interbreed. > 2) Can I use dd to verify my burns and avoid the readahead bug? You can try to skip over the bad spot in order to recover data blocks from blocks with higher addresses. After all it's a block device with random access reading. Nevertheless this will make any decent verifier raise the red flag. > 3) If not, how can I verify my dvd burn? The question is rather how you can burn a thoroughly readable DVD. To me it looks that your verifier did a good job. Congrats. Have a nice day :) Thomas -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
