Re: Announcing cdrskin-0.4.4

[Bill Davidsen <davidsen@tmr.com>]

Thomas Schmitt wrote:
> Hi,
>
> i wrote:
>   
> > > Like: 1 hour 40 minutes is too long for a backup window.
> > >       
> Rob Bogus wrote:
>   
> > That I can accept, I was going to post something similar.
> >     
>
> This all would be no issue if there was an alternative
> to BD-RE media like there are alternatives to DVD-RAM.
>
> I tested DVD-RAM, said "blargh", and decided to use
> DVD+RW.
>
> With re-writeable BD one has to craft "BD+RW" from BD-RE.
> Even then it lasts nearly an hour to fill a BD disc.
> (Reminds me of my first 2x Yamaha CD-RW burner.)
>
>
>   
> > > Or: The media are perfect and never ever show any bad spot.
> > >       
> > That sounds like a fairy tale.
> >     
>
> If the media would be as good as DVD+RW on my various
> drives then it would be ok for backup purposes.
>
> A severe problem is the larger size of BD media.
> Assumed similar probability of write failures per MB,
> you have to expect at least 5 times more misburns
> than with DVD+RW.
> That would be indeed unbearable.
>
>
>   
> > Ideally a copy of the backup would be held for byte-by-byte verify, and bad
> > spots (only bad spots) would be rewritten. That assumes that they CAN be
> > written successfully eventually. All solutions are ugly.
> >     
>
> I recommend multi-copy backups for long term archiving.
> I.e. identical images on several media all covered by
> the same list of block checksums (64 kB blocks).
> But that needs buffer storage on hard disk in order to
> truely get identical copies.
>
> Buffer storage for 25 GB is not appealing. Especially
> since i recently got rid of buffer storage for
> oversized files.
>
>   
Having a large buffer for large backups may be the only practical 
solution. I do use dvdisaster software for critical backups, it 
occasionally really saves the day, although it is slow when calculating 
the ECC codes to burn. Combined with dual layer DVD to reduce the number 
of media changes I can do practical backups.
> My usage scenario for a full speed BD-RE run would
> be short term backups which are allowed to fail
> from time to time. Not too often.
>
>
> If BD-RE with defect management is as ill as DVD-RAM
> on my Philips drive, then it is no real solution either.
>
> Imagine the backup operator sitting in front of a
> gnawing drive since hours. Pondering whether to finally
> abort the backup or whether to hope for the normal
> lame speed to come back.
>
> DVD-RAM is nearly unusable for me. If BD-RE is as
> bad, then i'll need to buy a tape drive for the next
> generation of backup media.
>
> My disk is 500 GB and my backup media are less than 5 GB.
> One can do a lot with multi-volume and incremental.
> But finally the backup data need to get onto media in
> a reasonable time.
>
>   
I don't know what external drives cost in Europe, they are about $130 
for 500GB in the US. That makes verified backups pretty cheap for 500GB. 
The cost effective solution for too much cheap disk may be more cheap 
disk. The cost of BD media is coming down slowly, but that is still far 
less cost per GB than the disk drive.

I burn "most critical" data on DVD for off-site backup, but daily still 
goes on those USB drives.
> So if it is possible to run BD-RE at 9.5 MB/s without
> too many misburns, then it is better than nothing.
> Still not good, i confess.
>
> I hope Giulio will tell us about his experiences.
>   


--
Bill Davidsen <davidsen@tmr.com>
 "Woe unto the statesman who makes war without a reason that will still
 be valid when the war is over..." Otto von Bismark