[vcf-midatlantic] several things

Dave McGuire mcguire at neurotica.com
Tue Dec 31 13:50:54 EST 2019


On 12/30/19 6:36 AM, Mark Whittington via vcf-midatlantic wrote:
> Regarding DVD-R, it's my understanding that most (if not all) optical
> formats are susceptible to physical degradation.  My current archival plan
> involves using external HDD's.  Given that you can buy a 5TB USB 3.0
> external drive for ~$140 and it will hold approximately 1000 4.7GB DVD-R's
> worth of data, it's economical as well as more reliable for long-term
> static storage.

  If you look at the error rate specs and do the math on those drives,
things don't look so good past 3TB or possibly 4TB.  Bits WILL get
flipped, you don't have to move very much data to see it happen, and
there's nothing you can do about it.  Remember, those drives are mostly
being churned out for consumers to store movies and huge video games
on...where a flipped bit here and there might result in one pixel's
color being off in one frame, or the tiniest little "tick" of static in
the audio.  Worst case, a movie file gets corrupted, and the usual
solution is "just download it again".

  For archival or first-source storage this obviously doesn't work.  I
frequently work with multi-GB datasets, and since they're generated
here, I can't "just download it again".  And in that world, every bit
actually matters.  Similarly, in some other networks that I manage, one
is a retail store chain (sales data, inventory data) and another is an
office full of accountants (tax data), every bit matters.

  The solution here is mirroring and checksumming filesystems (i.e.,
ZFS) and limiting spindle sizes (and thus error rates).  I myself will
not go past 1TB for 2.5" drives or 3TB for 5.25" drives.  I store all of
my data in ZFS arrays with at least ten spindles in each.  If I need
more storage, I add more drives.  Eventually drives in that capacity
range will become unavailable, but I'll cross that bridge when I come to it.

  All I'm saying here is be careful, actually READ the specifications,
and understand the markets that those drives are built for.  The number
of people out there who are watching movies and playing games dwarfs the
number who are working to archive important data.  This says a lot about
our society in general, which makes me want to vomit, but that's beside
the point and that reality is reflected in the products which are
offered to all of us.

              -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA


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