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Old 01-18-2003, 01:40 PM   #1
slackerboy
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Cool CD/RW capacity limits


Hi gang,

I need to know if in Linux one can format a cd/rw
higher than in Windows. For example, I have seen
that one can format a floppy at 1.88 MB. By the
same token, is it possible to format a cd/rw of
700 MB to a capacity higher than ~539 MB? I used
to buy the 650 MB cd/rw but after formatting it,
the capacity is about 539 MB, a whopping 111 MB
loss.

I bought some cd/rw of 700 MB/80 min and now
my HP8200i cd writer cannot use more than about
539 MB in Windows. Apparently, this is a limit
imposed by both the software and the hardware?
Thanks in advance.
 
Old 01-18-2003, 03:58 PM   #2
NSKL
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I have no idea what you are talking about. I never burned any CDs in windows, so i can't help you there, but in Linux when i burn CDs i can always use all of the space on it, be it 650MB or 700MB, both for data cds and audio CDs. Also what do you mean by formatting a CD? Something like mk2fs /dev/cdrom? I don't think that will ever work...
I wasn't much help, but i seriously don't know how you kill 111MB of a cdrom by "formatting" it...
-NSKL
 
Old 01-18-2003, 03:58 PM   #3
nxny
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539 MB is about right on a CDRW, becuase the formatted physical area wheere you can write data is smaller than the corresponding area in a CDR. You cant go further than that!! I think how the floppy driver achieved the feat is by laying the tracks closer, because you have more control over the floppy head ( tracks are much farther than they are in a CD, but a CD is much more fine-grained and you cant optimize it further and still read reliable data ). So if you tried real hard, I think you could fit 2.00MB into a floppy. But the chances that you can do that repeatedly, conistently and reliably reduces exponentially.

I see that you live in the US, where costco sells 100 CDRs for $14.99!! that's 15 cents a piece, so maybe you shouldn't worry about getting another one of those. Or get a DVD+RW if you want to backup huge chunks of data. I have an HP DVD+RW 200i.
 
Old 01-18-2003, 04:03 PM   #4
NSKL
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Well if there is only 539MB of usable space on a CD, how come then i can import over 600MB of files into a burning program (Take Eroaster for example) and burn the data CD, no problem, and i will have all my 600 MB on the disk i just burned? I don't know much about the way CD burning works, but if you say 539MB is the limit of the CD, and i fit 600MB on it, there must be something i'm missing..
-NSKL
 
Old 01-18-2003, 04:12 PM   #5
bulliver
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They are talking about cd/rw's not cdr's. Also, keep in mind that an audio CD consists of 2352 byte sectors - as opposed to 2048 bytes needed for data. So you can fit more data on a cd than the equivelent 'size' of audio.
 
Old 01-18-2003, 04:19 PM   #6
NSKL
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I see now, i missed the part about cdrw's not cdr's when i read the post the first time... Now it all makes sense
Thank you!
-NSLk
 
Old 01-18-2003, 05:25 PM   #7
michaelk
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When you mean format are you talking about packet writing i.e. DirectCd?
 
Old 01-18-2003, 07:55 PM   #8
slackerboy
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Michaelk,

Yes, I just used DirectCd on a 700 MB cd/rw and got 571 MB
reported as available. This was using Win 95 B

I have not tried yet to see how much space I would get in
Linux. I am reading as much as I can on how to use a cd
recorder in Linux and hopefully I will find out soon. Thanks everyone!
 
Old 01-18-2003, 09:17 PM   #9
nxny
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Quote:
Originally posted by michaelk
When you mean format are you talking about packet writing i.e. DirectCd?
The reason DirectCD is able to write more onto a CDRW is because it uses the UDF filesystem instead of iso9660, the universal CDROM filesystem standard. For more info..
http://www.trylinux.com/projects/udf/
 
Old 01-18-2003, 10:08 PM   #10
MasterC
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Ok, well I am still totally lost... A CDRW can only write up to 539MB of data even though they are listed at 650mb? I don't really follow. I seem to have no problem writing 650mb of mp3's to my cdrw's for playback in my truck stereo. Would this be because I've never formatted them using something like DirectCD and just write to them and erase them with:
cdrecord dev=x,x,x speed=x erase=fast

I've used erase=all before, and still seems to be able to use 650...

Sorry if I seem thick on this one, but this just seems very odd to me?

Thanks
 
Old 01-19-2003, 10:26 AM   #11
michaelk
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My only guess is that Roxio has not updated there DirectCD formating process for 700mb CD-RWs.

Formating for DirectCD is similar to formating a hard drive or a floppy drive. For example the actual floppy disk unformatted size is 2.0 mb but the formatting process requires overhead for the FAT tables etc so whats left is only 1.44mb. I would say that since you get 539mb for both 650 and 700 CD-RW's is just due to the DirectCD formating process. If you mount a DirectCD on linux you will be able to see several files. One of them is UDF.exe (or something like it.) This program will allow PC's without DirectCD to install a driver to view the contents.

Audio CD's do not have a data filesystem associated with them therefore you can record to the maxium capacity of the media.

BTW most default kernels do not inculde UDF support.
 
Old 01-19-2003, 02:08 PM   #12
nxny
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Quote:
Originally posted by MasterC
Ok, well I am still totally lost... A CDRW can only write up to 539MB of data even though they are listed at 650mb?
Thanks
Makes sense to me. cdrecord treats the CDRW just like a CDR ( except that you can erase the contents and rewrite ) whereas DirectCD/UDF have to format the disk. So say if you have 650 MB of mp3s in an iso, cdrecord knows where each and every bit is going to go even before it starts writing. Compare this to packet writing, where you can drag and drop files/folders( in windows) and use it just like a (slow )hard-drive. When you can use an infinite number of sessions to write to the disk, you have to have tracks laid out on the disk already, so that all the driver has to do is to lay it on top of the track. In other words, when you use packet writing, you there should be something *on the disk* that keeps track of where you're going write the next bit so that the same DirectCD can be written to by multiple computers. When you use Session-at-once, that overhead goes away and you get to use more physical disk space.

I have used CDRs with DirectCD too. If I remember right, when they came up to something like 570MB UDF formatted. But the penalty is that if after writing three 100MB files you decide to delete one, the 100MB that's supposedly freed by the delete operation cannot be reclaimed. Or the disk capacity is reduced to 570 - 100 = 470MB.

HTH
 
Old 01-19-2003, 03:11 PM   #13
MasterC
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Ok, I see. So you are saying it's a limitation of formatting the CD with DirectCD not with the medium itself? Is that a semi-correct assumption? So when I use mkisofs to build my iso that cdrecord will burn, there is some overhead, but nothing compared to when using DirectCD to format and "packet write" my discs.

So the UDF filesystem that DirectCD creates to enable the packet writing, takes up that much overhead that you lose on writing actual data to your disc, where if I create an iso then burn it to the disc, I will be able to use much more of the discs total size.

Would that be close?

Thanks!
 
Old 01-19-2003, 05:42 PM   #14
nxny
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Quote:
Originally posted by MasterC


So the UDF filesystem that DirectCD creates to enable the packet writing, takes up that much overhead that you lose on writing actual data to your disc, where if I create an iso then burn it to the disc, I will be able to use much more of the discs total size.

Would that be close?

Thanks!
Right on.
 
Old 01-20-2003, 01:41 AM   #15
yngwin
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Quote:
Originally posted by nxny
I have used CDRs with DirectCD too. If I remember right, when they came up to something like 570MB UDF formatted. But the penalty is that if after writing three 100MB files you decide to delete one, the 100MB that's supposedly freed by the delete operation cannot be reclaimed. Or the disk capacity is reduced to 570 - 100 = 470MB.
If that is true, then why would anybody use UDF at all? You have such a high overhead, you can't reclaim deleted space! You'd be better off just using iso9660 with multi-session!
 
  


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