What's with CD-RW?

[Duncan Farrow]

On 20/7/03 9:05 AM, in article
1fye6fs.13prxwuejm194N%dwright@metz.une.edu.au, "Denis Wright"
<dwright@metz.une.edu.au> wrote:

> GCZ <gcz@optusnet.com.au> wrote:
>

>> Plain non-rewrite CD's are really cheap - I don't see what the big problem
>> is.

>
> I think you have to be prepared to use your CD burning capability in a
> different way from a zip disk or floppy. There DO seem to be issues with
> writing multiple sessions and maybe the time will come when someone
> builds into the operating system the ability to use a CD pretty much
> like a zip disk. But until that time, your best bet is to do your
> backups on zip disks or remote system until you have enough data on them
> to warrant burning a CD. I agree with GCZ that once-only writable CDs
> are the best bet for this form of storage, with a limited number (say a
> maximum of 3) of sessions on each.
>
> Denis
>

I have found a partial solution for my situation using Toast 5.2 (Titanium).
You can do incremental backups using ISO9660. This means that a CD-R will
slowly fill up as files that have changed are added to the CD. For example,
I have about 200MB in my documents and mail folders. Over the course of a
few days, about 12MB worth of data changed. Thus, the CD now has 212MB of
space used leaving nearly 390MB to go. This works with either CD-R or CD-RW.
Obviously, once you have filled a CD-R, you need to create a new incremental
backup disk. I guess with a CD-RW, I could erase it and start again (haven't
done this yet).

Cheers,
Duncan.

[Duncan Farrow]

Mr Dewsons wrote:

>
> In article <3F1FDEB3.5C0925F6@iprimus.com.au>,
> Duncan Farrow <duncanfarrow@iprimus.com.au> wrote:
>

> > Mr Dewsons wrote:

> > >
> > > In article <BB4328F9.147B%duncanfarrow@iprimus.com.au>,
> > > Duncan Farrow <duncanfarrow@iprimus.com.au> wrote:

> >
> > === SNIP ===
> >

=== SNIP Again ==

> > Not sure what you mean about 'waste'. Under incremental backup, only
> > those files that have changed are added to the CD. Thus, if you have
> > used 200MB of available space on a CD-R and 20MB worth of files have
> > changed since your last back up, 20MB extra gets burned meaning you
> > have now used 220MB of space. It is only the space taken up by the
> > original files that becomes wasted. At least, that's my understanding.

>
> I remember reading in the Toast manual that when you write the first
> session of a disc, you lose 22 megs off it. So if you've got a 1 meg
> file written to the first session, that session will take up 23 megs.
> Any subsequent sessions will take up at least 12 megs - it'll be 12 megs
> plus whatever the size of the files is.
>
> Haven't you ever looked at the bottom of a multisession disc and
> actually been able to see the space in between sessions?

No I haven't and I misunderstood your earlier remarks. Next time
I do an incremental backup, I'll make a point of looking at the
space used.

Cheers,
Duncan.