Greg 'groggy' Lehey
grog at FreeBSD.org
Fri Aug 5 04:39:52 GMT 2005
On Wednesday, 3 August 2005 at 14:51:06 +0200, cpghost wrote:
> On Tue, Aug 02, 2005 at 10:22:19AM +0930, Greg 'groggy' Lehey wrote:
>> of coasters, and it might help identify the issues. All my burn
>> failures (about 40% of total!) have been with DVD+Rs, though
>> admittedly a cheap no-name brand bought in Taipei. I've found that
>> they work OK if I burn them at speed=1; if I use the default speed of
>> 4, they usually fail.
> Same here. DVD+R fail for me at a similar rate, though DVD-R from
> the same brand are doing just fine.
> What's puzzling is that growisofs doesn't always notice errors
> while burning. Approx 1/3rd of errors are first detected while reading
> the DVD+R back in (MEDIUM ERROR READ BIG etc..). OTOH, I'm adding and
> later checking md5 checksums for every file; and I've never had a
> checksum mismatch. If something goes wrong, it's the whole reading of
> a sector or a bunch of sectors.
I don't think that's puzzling. Writing doesn't imply reading; if the
drive thinks it has written the data, you can't find out whether the
medium has also stored it until you read it back. You'll note that
the script I mentioned (http://www.lemis.com/grog/making-AUUGN.html)
includes a separate verify step. Based on my experience (and yours
:-), I'd strongly recommend always verifying.
New discovery about ISO file systems (today): you can burn symlinks to
DVD, and they'll work under FreeBSD and Linux. They fail under
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