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CD R/W Mystery

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9 replies to this topic

#1
thecavern

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Hi,

I have a question that perhaps someone can answer.

I backup files on a CD-RW which is supposed to 700MB.

I update the disc about every six moths -- IF IT LETS ME !!

The problem is : When I insert the disc I can't add or delete any files. The reason, reviewing "properties", is that
the disc has used 435MB and NO free space is left !!

(There is no problem copying the files to another location)

This has happened before and I wind up inserting a clean disc and copying everything to a new disc.

I can't figure out how this occurs.

Does anyone have a clue ??


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#2
jaclaz

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Hi,

I have a question that perhaps someone can answer.

I backup files on a CD-RW which is supposed to 700MB.

I update the disc about every six moths -- IF IT LETS ME !!

The problem is : When I insert the disc I can't add or delete any files. The reason, reviewing "properties", is that
the disc has used 435MB and NO free space is left !!

(There is no problem copying the files to another location)

This has happened before and I wind up inserting a clean disc and copying everything to a new disc.

I can't figure out how this occurs.

Does anyone have a clue ??

Which program/tool (and under which OS) are you using it to write on the disc?
How EXACTLY are you using it?
If you are using "multisessions" or by any chance the disc become "finalized", you will have NO available space on it, no matter how much data is on it, but since it is an RW, you can make a copy of the files on it, re-initialize the disc and copy back the old and new files anyway.

jaclaz

#3
thecavern

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When I back up a file/files, I right click on the file or folder. I then pick "Send To" and
pick the drive that the CD RW is located.

So I'm not using a program as such.

I'm on Vista.

Edited by thecavern, 08 November 2012 - 02:25 PM.


#4
jaclaz

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I am not an expert on this, but it seems like Vista uses the IMAPI 2 to write discs in SAO mode, see:
http://en.wikipedia....recording_modes
http://en.wikipedia....e_Mastering_API
http://www.osta.org/...ology/cdqa2.htm
which is basically a multi-session disk :unsure:.
It is likely that the issue you are having are created by the multiple sessions indexes, lead-in, lead out, etc..
Are you positive that you are using CDRW media (and not CDR) ?

jaclaz

#5
thecavern

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Definitely a CD R"W".

#6
jaclaz

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Have a look at one of those CD's with a tool like Isobuster (freeware/shareware):
http://www.isobuster.com/
you will like find a number of "sessions".

jaclaz

#7
Ponch

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It is likely that the issue you are having are created by the multiple sessions indexes, lead-in, lead out, etc..

If I remember well, each session uses more than 30MB of the disc, additionally to the included data.

#8
thecavern

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"Isobuster" is designed to retrieve "lost data".

Assuming that the CDRW has a lot of space wasted on deleted files, I thought I'd look around
for a way to compress the CD but haven't found any way to do that.

Perhaps there is a way ?

#9
submix8c

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No... IsoBuster has multiple functions, INCLUDING viewing to see IF you have more than one Session.

Someday the tyrants will be unthroned... Jason "Jay" Chasteen; RIP, bro!

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#10
jaclaz

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"Isobuster" is designed to retrieve "lost data".

NO, it isn't or it it isn't "only" for that.


Assuming that the CDRW has a lot of space wasted on deleted files, I thought I'd look around
for a way to compress the CD but haven't found any way to do that.

That's normal as there isn't any.

Perhaps there is a way ?

No, there isn't, the way you have ben doing it.

The way you have "backed up files" till now is "wrong" in the sense that you are using a feature of the OS that is NOT aimed to create "efficient", "compact", results.

If you take some time to read about SAO writing mode, this would become evident.

Imagine that you work in a (crazy :w00t: ) company delivering (say) TV's.
Your job is to load on a truck a TV (in it''s box), drive the truck, get to the customer house, unpack the TV and deliver/install it.
Noone ever disposes of the empty packagings that remain on the truck.
You will soon find out how once you have delivered a small number of TV's you cannot load anymore a (filled) Tv's box on the truck as all the space is occupied by the empty boxes.

Now what a SAO writing approach behaves is more or less like this:
  • you package the initial (first sesson) files in a (virtual) cardboard box complete with polystirene fillings
  • you load the box on the CD
  • on next session you take the contents out of the first box, and add them together to some new contents to a new, larger box
  • you load this second box on CD
  • and so on
  • soon the CD will be full of empty smaller boxes and one large box, this latter being on top of all the other ones and the only one you can open and access, and that contains all what was once stored in the "previous" boxes

Just as it is in the case of the truck, the right "strategy" is to put aside the filled box, empty the truck, then load again the larger "last" (filled) box on the truck.
Translated it means:
  • copy (temporarily) the CDRW contents on another media (hard disk)
  • re-format/re-initialize the CDRW disc
  • copy back to it the temporarily copied contents

The alternative being used a "packet-writing" software/tool that allows to add data to a CDRW with less "overhead" (but this solution is less than optimal because of possible later reading issues of the CDRW).
Some other news (good or bad it's up to you to decide) is that Optical media (like BTW *any* media) is not particularly reliable in the long term, and particularly "standard" recording apps and CDRW media are not the best choice.

Burning apps dedicated to create backup media store additional (redundant) information on the media so that in case of mis-readings the errors are more likely to be corrected.

As an example Infinadyne makes a (Commercial) tool called Accuburn-R:
http://www.infinadyn...accuburn-r.html
which adopts - among others - this "better be safe than sorry" approach.

But there is also an excellent Freeware/Open Source tool, DVDisaster:
http://dvdisaster.net/en/
to the same effect.

jaclaz




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