Re: [Dvdrtools-users] DVD+R/+RW support

[Volker Kuhlmann]

> >Unfortunately DVD-RAM doesn't have any sort of profile in the market 
> >which is worth mentioning,
> 
> That is a commonly poor assumption.

From my point of view (home + small business user) I have to disagree. A
quick count of local shops' online catalogs gives:
shop A: 12 different DVD burners listed, not one with -RAM
shop B: has 2 or 3 iomega DVD-RAM capable burners
It's possible they didn't add -RAM to their feature lists, but neither
sells -RAM media. It's clear that DVD-RAM essentially doesn't feature.

Perhaps in the highly professional area it's different, but even there I
doubt volumes are high. Out of interest I might ring a few more shops
next week though.

> DVD-RAM was first.

Come on, that says nothing about its popularity, performance, or
expected time of "being around".

> DVD-RAM will still be around and supported  when DVD+RW and DVD-RW have 
> been replaced by BlueRay and others.

A prediction. Might well come true...

> Those who care about longterm backups know all about it.

I don't think the issue of long-term backups are all that simple.
Longevity studies of optical media seem to have become rather rare since
the mid/late 90s. Verbatim has one online for their DVD+R 4x. There are
other solutions too, depending on circumstances. If I have fewer than
say 20 DVDs, I can easily copy them onto new media every 2-3 years, and
the somewhat better consumer DVDs (not talking Princo here) will last
that long.

Do you have any pointers to useful longevity information for any of the
5 DVD formats we've been talking here? I'd be very interested.

> > nor how to use it under Linux.
> 
> Stick in DVD-RAM disc.
> Mount (or let your distro automount it if it does).
> As Nextel says ... Done.

Oh, I didn't realise that. How does it work? Does the drive handle the
filesystem? Why do you still need udftools then?

You're not talking about the kernel's packet writing? That would work
with the same steps as above for DVD+RW, and with any filesystem. The
problem there is that the performance of Linux udf precludes any
practically usable application (even when ignoring reliability issues).
Perhaps it works in the case of very few very big files, but as far as
eg the files in $HOME are concerned, it's not usable. Well that was my
result of an initial speed test on kernel 2.4.~18 anyway. And it wasn't
that easy, documentation was and is non-existant.

> "Raw" MO is good maybe 3 years, assuming you don't get an error in the 
> original write.
> That's the primary problem, only solved by proprietary MO, then PD-CD, 
> then DVD-RAM.

You lost me here. MO is magneto-optical?, but what are the connotations
of it, ie what other info is "MO" supposed to communicate to me?

> You have to understand how ROM/WORM works compared to MO, which explains 
> why CAV MO in a legacy CLV drive or with CLV MO media causes all sorts 
> of issues.

Do you have any pointers, or even a quick summary?

> But the lack of a WORM +R really hurts not only its compatibility, but 
> longevity.

WORM is once-writable here? But there is a DVD+R? I don't understand you
here.

> WORM has about the same write  error rate as magnetic, 10**13.
> MO is 10**9, 10000x worse.
> That's why DVD-RW and DVD+RW can't be trusted to long-term backup.

I'd never use erasable media for long-term, that's why I said "rolling
backups". They'll be good for a few months. Every so often it goes onto
non-erasable media.

> DVD-R WORM and DVD-RAM MO are the only standards with longeveity.

And DVD+R WORM?

> >Of course, any organised person verifies burnt disks after burning if
> >they're meant for the keeping, and I don't see a difference there
> >between +-R(W) or -RAM.
> 
> Of course you don't, because you don't know the difference between 
> single-groove pressed ROM and recorded WORM.

I don't know anyone who gets a silver disk pressed just for a backup,
but then I don't work in the military. For the 4 DVD-+R(W) formats (and
CD anything) it is always advisable to verify after burning. If DVD-RAM
has integrated automatic verify, then that's different.

> As most people have found, once you write more than a few times with 
> CD-RW, DVD-RW or DVD+RW, but lots of files in a FAT/NTFS and even some 
> inode filesystems, those 1,000 rewrites easily get eaten up with only 
> 10-25 full disc rewrites.

Sure, that's why that mode of operation is supposed to use a filesystem
which is easy on rewrites.

> And what Sony/Philips doesn't tell you is that DVD+R is really just a 
> DVD+RW MO disc that is less tolerant, not a WORM like DVD-R.

Interesting. Sorry for being cautious, but is this a fact or more a
well-formed opinion?

> MO's pie-slice v. WORM's ROM-like single groove is why DVD+R is not as 
> compatible as DVD-R.
> Players must know how to emulate the physical layout of MO like WORM, 
> and not even many Sony/Philips models did for a long time.

I'm not sure I follow you here. DVD+R is said to be the most compatible
for making DVD video disks.

> You'd be surprise how many times a MO writes incorrectly, but you don't 
> see it until a few reads later.

You mean the first read (or 3) would work, the next one wouldn't? Within
what timeframe?

> UDF works fine for me.
> It was really design for DVD-RAM.
> I get as sustained 3.8MBps.

On a single humangeously big file I believe you. What do you get for a
cp -a $HOME /mount/dvdram ? And a tar -cf- /mount/dvdram/. >/dev/null?
That's why I forgot about Linux udf after the first try. The read still
hadn't finished after >30minutes on a CD-RW - one word: useless. And the
kernel's block buffering tends to kill the machine on writes.

> What software are you using?

Growisofs. Overall burn speed is easily verifiable with a wall clock.
The burn went smoothly and without errors, there's no reason to assume
cdrecord-prodvd would do better. In fact a friend has the exact same
A106 an got the same media errors under 'doze.

I only bothered with dvdrecord once in my early days and it died with
some SCSI error. Since digging a bit deeper into the various dvdrecords
I consider them to be considerably inferior.

> I have no problem finding 1x and 2x media.

:) Not in my city.

> Most people who bought DVD+RW since 2000 have learned to regret it until 
> the 4th gens came out last year.

Everywhere I find DVD burners calssed into "generations". The annoying
thing is that there never is a description of what each "generation"
actually means/implies/defines/contains/newly introduces. It's therefore
communicating in a foreign language - no understanding until the
vocabulary is translated. I haven't found a useful translation yet.

> That's a *lot* of beta testers.
> At least DVD-RAM and DVD-R have been consistent since introduction.

Ack + ack. But as I said, matters less these days.

Thanks much for all your technical info, Bryan. Happy holidays everyone,

Volker

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Volker Kuhlmann                 is possibly list0570 with the domain in header
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