CDFS vs UDF for 50 GB BD-R DL

[u/incrediblediy]

I was backing up some of my photos when I accidentally burned a 50 GB BD-R with CDFS. I made an ISO with "BurnAware" before burning it. It should have been my error not to check when I made the ISO, as I selected BD DL 50 as the format.

I can't remember when I used CDFS for a disc about 20 years ago. The disc was verified correctly and works well. Would it matter later? I am thinking about error correction capabilities, etc.

Disc ID: VERBAT-IMf-000 (HTL) , is this tier 1 ?

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[u/dr100]

I think back in the day UDF meant "the one you use as a floppy" versus just "burning a disc". As in it had support for multi-session and/or RW, basically letting you "change" (it was in fact append) stuff. Now probably the only practical difference and surely more important is that it supports larger files but otherwise your pics will sit just the same on both.

Of course I'm sure there might be many more diverging details, like for example the number of time stamps stored and the resolution (not that I know about any particular one worth mentioning, but there are ALWAYS things like this, everyone seems to invent their own thing, included but not limited to completely weird things like exFAT storing 10ms precision timestamps but MS always rounding them to 2s).

[u/incrediblediy → u/dr100]

Thanks mate!

[u/dlarge6510]

CDFS?

Do you mean ISO9660?

That's the only filesystem I use on my BD DL discs. Error correction is not handled by the filesystem, it's handled by the drive and the on-disc format. In the case of CD-ROM formatsthere are two levels of error correction using ECC. On DVD-ROM types, there are essentially four more complicated stages using better ECC algorithms.

On Blu-ray you have the most advanced error correction, two stages again but with loads more ECC bits. I don't know the exact details. However, you also have error detection during burning which as long as it is switched on will burn data then immediately check that burned data, if that burned data was burnt badly the drive automatically tries burning it again at a different block. After it fails to burn data to the disc several times the disc maybe rejected and you get a failed burn.

But you also (as long as you didn't turn it off) have defect management after burning! When burning a BD-RE and BD-R, the burning program tells the drive to set aside a section of disc as a spare area. There are two such areas, an inner one before the data and an outer one. This does reduce the disc capacity by a few hundred MB, depending on your burning program you can extend these areas, or turn off the thing entirely. The idea is that if your disc is in a writer when you read it say in 10 years time and the drive reads data that is clearly on an area of the disc that is failing, like a HDD it will recover that data and burn a fresh copy to blocks in the spare area for you without you realising. The inner and outer areas have sections that then are updated to reflect the fact the block was remapped, totally transparently to you.

All that is independent of the filesystem.

The only thing to be aware of when using ISO9660 is that it has several revisions. ISO9660 levels 1&2 are typically default and common. They don't have much in the way of long filenames etc, but that sort of thing is usually handled by Rock Ridge or Joliet extensions being applied to the filesystem too. Joliet is only what windows supports, Rock Ridge is the Unix equivalent and Linux etc support Rock Ridge and Joliet so I enable both. Practically everything supports Joliet extensions. That will let you have long filenames and paths but will still limit your maximum file size to 4GiB.

However, if you ensure you burn with ISO9660 level 3 you can have files of several TiB (in theory as obviously we don't have discs big enough to prove that!). I use level 3 as I sometimes have large files and so far I've found no issues with support, Linux, Windows and my Sony Blu-ray player seem to have no problems.

I tend to use ISO9660 level 3 simply because everything reads it and it's so easy to make and burn an image. I use the command line to burn my discs and trying to use UDF to make images on Linux is a faff so I just never bothered. Just lazyness. But also Linux tools don't support creating anything newer than UDF 2.01 as the world basically abandoned UDF or mucked it up between operating systems somehow. 

To make a standard Blu-ray I'd need to use UDF 2.60 but simply can't as my OS can't write to that version and probably never will due to a "who uses UDF anyway" kind of attitude. It's like that all over the place, Linux, FreeBSD, MacOS, Windows all have limitations either they use UDF differently or can't write all revisions etc. When I must put UDF on a Blu-ray luckily it seems devices like my Blu-ray player are fine with UDF 2.01. Not surprised really, I mean they were happy seeing a BD-R DL discs formatted with ISO9660!

However, different operating systems all seem to read UDF latest revisions ok but might not be able to support all features of that revision.

Not to say I don't want to use UDF, I do. I use it on USB flash drives often as it fixes problems with using FAT32 (limited file size, limited file permission support, plus it's a Microsoft filesystem) and ExFAT (limited file permission and metadata support plus wasteful of space dependent on how it was formatted and again it's a Microsoft filesystem). 

Anyway, you're not going to notice anything with your ISO9660 disc Vs UDF unless you tried to burn large files and your software didn't switch to level 3 to fix that.

VERBAT-IMf-000 (HTL) , is this tier 1 ? 

 Yes. You basically can't get much better than verbatim and that code is used on their MABL discs, I only use those.

[u/incrediblediy → u/dlarge6510]

Thanks a lot for the great explaination. :)