[Table of Contents]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [ARSCLIST] Testing DVDs

Claus,

I think you may be under the impression that I am recommending LTO as
a long-term storage option.

As you know, all platforms (HDD, data storage tape, optical media)
will have to be subjected to a practice of supplemental migration.  A
reasonable window of 3-5 years is about the best that you can expect
with the advances in technology.  LTO has so far proven that they do
have a roadmap (LTO1/ 2/ 3/ 4/ 5/ 6) and continue to provide
backwards compatibility with previous generations.

Basically... for any archive that has to work within a budget, any
physically checking of media can be very expensive if one has to
invest in
hardware to accomplish the task... or hire people... I wouldn't
suggest
getting the guy from the "corner of the street".


"any physically checking of media" should be done by a professional
IT person, I would agree.  But that would appear to hold true for
those who deploy their own RAID array as well.  Depending on storage
amounts, a NAS or SAN won't be any cheaper than an LTO drive.
 I wouldn't let the "guy from the corner of the street" touch either
system, and there are costs involved either way.  LTO-3 WORM media is
currently about $0.25 per GB.

As an example... we consider ALL physical media as a future
problem. When we
archive for LTO we only use half the life expectancy of the drive,
in the
hope that future disaster recovery will benefit from us storing the
original
drive that generated the tape with the tapes... this is due to head
alignment etc...


I'm not quite sure that "storing the original drive that generated
the tape" is a useful approach unless you can store repair parts and
a technician that can repair the drive.  I would have the data off
the tape well in advance of the manufacturer's claimed life
expectancy.  And we have never had to "realign the head" on an LTO
drive.

Practically, we are located 250 ft underground... and have mirror
sites
around the US for physical separation.


You are lucky in that regard.  Most archives aren't underground and
DO have to consider geographical separation.

I have nothing against physical based storage, but my point is that
anything
that is based on physical assets will by default deteriorate over
time...

I hope this clarifies my statements... 

I have nothing against mirrored online backup sites!  However, your
point "that anything that is based on physical assets will by default
deteriorate" would seem to implicitly include HDD as well.

John Spencer
www.bridgemediasolutions.com


On Jun 3, 2005, at 1:12 AM, Claus Trelby wrote:

Hi John,

I use mainly LTO for my clients requirements, when it comes to
tape... with
great success so far...

Basically... for any archive that has to work within a budget, any
physically checking of media can be very expensive if one has to
invest in
hardware to accomplish the task... or hire people... I wouldn't
suggest
getting the guy from the "corner of the street".

As an example... we consider ALL physical media as a future
problem. When we
archive for LTO we only use half the life expectancy of the drive,
in the
hope that future disaster recovery will benefit from us storing the
original
drive that generated the tape with the tapes... this is due to head
alignment etc...

Practically, we are located 250 ft underground... and have mirror
sites
around the US for physical separation.

I have nothing against physical based storage, but my point is that
anything
that is based on physical assets will by default deteriorate over
time...

I hope this clarifies my statements...

Claus.

Claus Trelby
Managing Engineer/Partner

XEPA Digital
1137 Branchton Road, 19-N-3
Boyers, PA 16020-0137
www.xepadigital.com
ctrelby@xxxxxxxxxxxxxxx
P:724-794-3686
F:724-794-3292
C:805-490-1730



-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of John Spencer
Sent: Thursday, June 02, 2005 11:22 PM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Testing DVDs


Could you please elaborate on your statement:

"Even if you can check a disc type media physically I think it will
be hard to check something like
Exabyte or LTO on a regular basis without tearing the media apart..."

Disregarding Exabyte drives and tapes, LTO is the largest selling
data storage tape drive in the Enterprise IT environment,
and they seem to be pretty happy with it.  Most of the media vendors
do 1,000,000+ pass testing and are eager
to share the results (Fuji is very good about sharing their
information).  I agree that RAID is a great option, but
near-line solutions should be looked at as a potential part of the
digital archive process.

Geographical separation comes to mind in this instance.

John Spencer
www.bridgemediasolutions.com


On Jun 2, 2005, at 8:59 PM, Claus Trelby wrote:


Hi Peter (all),

Without going into physical indicators and complexities for disc
media
failure, I would just like to add a little suggestion to all of
this...

We want to preserve the data, right? A minimum of two different
types of
media for storage plus a checksum file such as MD5 placed in the
middle
storage area of the media (tape or disc) is our default... we then
spot
check all media periodically (especially edge content or all
content), and
any deviation from the checksum results in alerts... Even if you
can check a
disc type media physically I think it will be hard to check
something like
Exabyte or LTO on a regular basis without tearing the media apart...

Just a suggestion.... I've personally stopped paying attention to
accelerated media testing... I find it useless... history always
proves it
wrong...

I believe spinning/exercised RAID disc (HD) storage is the only way
to go...
still very expensive, but a couple of the companies I am consulting
for are
getting in the right ball park... less than $4 per GB (22TB
minimum)...

Claus.

Claus Trelby
Managing Engineer/Partner

XEPA Digital
1137 Branchton Road, 19-N-3
Boyers, PA 16020-0137
www.xepadigital.com
ctrelby@xxxxxxxxxxxxxxx
P:724-794-3686
F:724-794-3292
C:805-490-1730

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Peter@xxxxxxxxxxxxx
Sent: Thursday, June 02, 2005 7:43 PM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Testing DVDs


I will be attending the AES/ISO meeting of the Technical Commission
on Tape
and Disc preservation this coming week.  We have been discussing
ways of
testing DVD's and it is a subject that is part of next week's
agenda.  So
far, it is unfortunately true that the testing methods developed and
recommended are somewhat too cumbersome and time-consuming to be
widely
practical.  If we review any documents that offer reasonable
alternatives, I
will report such to the list.

One of the primary failure mechanisms that needs more testing is
delamination.  In my opinion, from review of the available data,
there is
not enough reliable information on the stability and reactive
properties of
the glue used to bond the layers together.  If someone has a good,
quick way
to test the glue stability, I would be pleased to pass it on to the
Commission.

One of the problems encountered (again, in my opinion) is that
testing for
new mediums tends to mimic the tests for previous mediums.
Accelerated
aging tests for recordable sound media were initially developed to
try and
test binder hydrolysis.  Discs are a very different animal than tape.
Polycarbonate disc surfaces do not hydrolyze like polyester binder
in tape.
On the other hand, reflective mediums in Discs can oxidize while
ferric
oxide recording pigments in older tape don't.  Again, the binder
mechanism
on tape is integral to the entire recording layer while Discs are
actually
held together with an added layer of glue.

It is quite possible that we need to seriously re-think the testing
parameters and methods for Discs.  Again, if anyone has some
suggestions, I
would be glad to pass them along.


Peter Brothers
President
SPECS BROS., LLC
(201) 440-6589
www.specsbros.com

Restoration and Disaster Recovery Service Since 1983



-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of seva
Sent: Thursday, June 02, 2005 9:38 AM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Testing DVDs


i think that querying Mitsui itself would yield more information.
they
have a sterling reputation and i'm sure would have no intention to
launch the gold DVDs without serious advanced aging tests of their
own...


David Lewiston wrote:



So there are plenty of brilliant comments, but no practical


suggestions for


doing a quick and dirty test?

Salutations, David L


----- Original Message -----
From: "Nigel Champion (ARTS ANT)" <n.champion@xxxxxxxxxxxxxx>
To: "David Lewiston" <david.lewiston@xxxxxxxxxxx>
Sent: June 01, 2005 4:35 PM
Subject: RE: [ARSCLIST] Gold DVD-Rs


Then you need to repeatedly insert and remove the DVD-R from its'
case.
This is to find how long it takes to separate the two polycarbonate
layers of the DVD!

Regards
Nigel






--
salutations,
seva

www.soundcurrent.com
|| | |  |   |     |        |             |                     |

Things are not what they seem to be; nor are they otherwise.
   -- Lankavatara Sutra





--
No virus found in this incoming message.
Checked by AVG Anti-Virus.
Version: 7.0.322 / Virus Database: 267.4.1 - Release Date: 6/2/2005

--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.322 / Virus Database: 267.4.1 - Release Date: 6/2/2005




--
No virus found in this incoming message.
Checked by AVG Anti-Virus.
Version: 7.0.322 / Virus Database: 267.4.1 - Release Date: 6/2/2005

--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.322 / Virus Database: 267.4.1 - Release Date: 6/2/2005



[Subject index] [Index for current month] [Table of Contents]