16 Mar
2005
16 Mar
'05
9:29 a.m.
From: Saquinn624 at aol.com
Coming in on this a little bit late, but if you haven't checked out the
Library of Congress you should.
www.loc.gov/preserv gives you a basic run down of ways to care for archived
materials, and the NIST/CLIR puts out Special Publication 500-252 "Care and
Handling of CDs and DVDs - A Guide for Librarians and Archivists" (e-version
available). Other tips- gold disks, AZO dye are reputed to last longer.
The phenomenon of failure from the outside in has interesting possibilities-
have software write a known pattern in the outermost section of the disc and
pop up a warning when it starts to deteriorate. Hopefully this would give
enough time to move data to another disk.
- Scott Quinn
Hi
This does require regular reading of the archived disk. This
is not necessarily an easy thing to do.
Dwight
17 Mar
17 Mar
12:32 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
On Wed, 16 Mar 2005, Dwight K. Elvey wrote:
This does require regular reading of the archived
disk. This
is not necessarily an easy thing to do.
I'd like to offer that there is no such thing as archival computer
media. None.
Dwight's comment is succinct; all offline storage needs to be
checked. Literally all of it is rotting on the shelf.
(For short-term backup, eg. data loss prevention, this logic
doesn't apply so directly.)
It's a lot of work to check archival data; nearly no one does it
right, and it mostly amounts to spot checks (a valid method
certainly but in itself an admission of the scope of the problem).
I don't do "backups" per se; I keep everything on rotating
spindles, aka hard disks in running systems. If you pause to
consider what this means as a long-term solution, it sounds really
precarious, because it is; but in fact it's *less precarious* than
any form of offline storage because it is essentially 100%
continuously monitored, embedded in a live computer.
I have five computers in four physically distinct locations (three
are >> 100 miles apart) with enough storage to hold literally all
the computer-readable data I own.
If you somehow think that tapes stored in a controlled vault is
more reliable, or less susceptible to bit rot than rotating
spindles, I believe you are wrong (and my every experience and
observation says otherwise). Only fiche and paper are statically
reliable.
It's no crazier to think that my data (sic) will reside on a
series of continuously operating computers for the next N decades
than it is that a CD-R or DVD-R will last as long, or be readable
N decades in the future.
Yes, in one sense it makes me nervous. That's good! Dump tapes
sitting in a closet or bank vault are rotting and becoming
spectacularly incompatible; it just doesn't generally make people
nervouse, but it should.
Hard disk storage also neatly avoids the incompatible-media issue;
it's continuously ported, incrementally. The translation issues
are from M to M+1, far less than trying to deal with 8" floppies,
1/2" tape or other once-standard media.
Also, for the moment at least, disks of tomorrow are chealer and
larger than disks of today, neatly taking care of increasing data
size (for how long this will hold out I don't know).
Whether you have 10MB or 1 TB of data, it's still cheaper with
rotating spindles. If you've really got a terabyte of data to
reliably save, backup tape isn't cheaper -- if you include the
longevity issue, of translating last-years tapes to next-years
tape. Who does that? Not many...
It's not about the medium, it's about the data. All of our mediums
suck for archival purposes, except paper and fiche.
Generally-speaking, our cultures don't directly care about
preserving the future, and machine media is a narrower case of
that.
16 Mar
16 Mar
11:51 p.m.
New subject: archiving data, was RE: Media Longitevity/Care
On Thu, 17 Mar 2005, Tom Jennings wrote:
On Wed, 16 Mar 2005, Dwight K. Elvey wrote:
Your experience may differ, and you make very valid points and I dispute
none of them. However, I find that media is much more sturdy than these
discussions would indicate. We tend to gripe very loudly (and rightly so)
when poor quality backup media takes our data with it. But what about all
those times we go back to our old backups and thankfully find what we
need?
I consistently read lots of data with nary a problem: 20-30 year old
floppy disks (5.25" and 8"), 20-30 year old mag tapes, even 20 year old
VHS tapes. And of course the punch cards don't count ;)
I wouldn't doubt that newer media like CD-R has problems, but as long as
you make incremental backups and also do as Tom says and keep your data
"live" you should be fine. It also helps immensely in how you store your
media. In a safe, dry, dark place that doesn't get wild temperature or
humidity fluctuations: good deal. In a barn: not so good.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
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This does require regular reading of the archived
disk. This
is not necessarily an easy thing to do.
I'd like to offer that there is no such thing as archival computer
media. None.
Dwight's comment is succinct; all offline storage needs to be
checked. Literally all of it is rotting on the shelf.
(For short-term backup, eg. data loss prevention, this logic
doesn't apply so directly.)
It's a lot of work to check archival data; nearly no one does it
right, and it mostly amounts to spot checks (a valid method
certainly but in itself an admission of the scope of the problem).
I don't do "backups" per se; I keep everything on rotating
spindles, aka hard disks in running systems. If you pause to
consider what this means as a long-term solution, it sounds really
precarious, because it is; but in fact it's *less precarious* than
any form of offline storage because it is essentially 100%
continuously monitored, embedded in a live computer.
I have five computers in four physically distinct locations (three
are >> 100 miles apart) with enough storage to hold literally all
the computer-readable data I own.
If you somehow think that tapes stored in a controlled vault is
more reliable, or less susceptible to bit rot than rotating
spindles, I believe you are wrong (and my every experience and
observation says otherwise). Only fiche and paper are statically
reliable. 
17 Mar
17 Mar
11:52 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
However, I find that media is much more sturdy than
these discussions
would indicate. We tend to gripe very loudly (and rightly so) when
poor quality backup media takes our data with it. But what about all
those times we go back to our old backups and thankfully find what we
need?
In this vein, I recently dragged out an old Sun QIC drive to read a
friend's tapes.
The tapes must have been written something like 15 to 20 years ago,
probably taken moderately but not especially good care of since then,
and I can't recall any problems. (It was only several tens of
megabytes, so it was no problem to shovel it around today once I had
the bits on disk.)
/~\ The ASCII der Mouse
\ / Ribbon Campaign
X Against HTML mouse at rodents.montreal.qc.ca
/ \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
1:35 p.m.
New subject: archiving data, was RE: Media Longitevity/Care
Perhaps it's just me, but I have stacks upon stacks of
5.25" floppy disks that have been around since ~1981,
still used regularly, and have yet to see one fail.
Mostly Janus, Nashua, and Verbatim DataLife DS/DDs.
However, it seems to take only my being within 15 feet
of a 3.5" floppy to corrupt the data on it, even if
it's a brand new disk...
However, I am a tad concerned about what will happen
to our prized hobby when such items as 9-track tapes,
TK50s, and TU58 DECtape-IIs truly become absolute
unobtainium. I suppose our good friend Warren will
probably continue supplying us with VTserver for
console boot media, but there's just nothing quite
like loading up The Real Thing (tm)... A huge part of the
retrocomputing experience for me, personally. Especially
9-track open-reel tapes...
I'm not even going to go into the availability of such
items as RD54s and RA81s... too depressing for a rainy
windy afternoon in the southwest...
John
der Mouse writes:
> However, I find that media is much more sturdy
than these discussions
> would indicate. We tend to gripe very loudly (and rightly so) when
> poor quality backup media takes our data with it. But what about all
> those times we go back to our old backups and thankfully find what we
> need?
John P. Willis
11:53 p.m.
New subject: archiving data, was RE: Media Longitevity/Care
On Thu, 17 Mar 2005 08:51:42 +0100, Vintage Computer Festival
<vcf at siconic.com> wrote:
Your experience may differ, and you make very valid points and I dispute
none of them. However, I find that media is much more sturdy than these
discussions would indicate. We tend to gripe very loudly (and rightly
so)
when poor quality backup media takes our data with it. But what about
all
those times we go back to our old backups and thankfully find what we
need?
I think the problem is that arcival quality is a very demanding thing. 99%
reliability jus is not good enough for that, but it is plenty for most of
us. You just do not rely one a single copy.
You can always read things most people would just write off if you're
willing to pay.
IBAS will read your erased disks and tapes, even if severely fire or
chemically damaged.
Just getting an estimate will cost you a few thousand dollars, though.
--
Bj?rn
18 Mar
18 Mar
1:23 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
[a bunch of replies all in one]
On Wed, 16 Mar 2005, Vintage Computer Festival wrote:
My assertion is that it's a false economy; besides bit-rot,
there's future (near-guarenteed) incompatibilities, and if enough
time passes in multiple media (papertape... 1/2" mag tape...
DC300... 3740... QIC... etc)
In fact, with Moore's Law and related continuous hard disk is *far
cheaper*. It's just that you're not deferring the cost to your
future inlaws!
No point in insuring the data contained in the disk drives in the
computer in the back seat; it's just a copy.
On Thu, 17 Mar 2005, Doc Shipley wrote:
However, I find that media is much more sturdy than
these
discussions would indicate. We tend to gripe very loudly (and rightly so)
when poor quality backup media takes our data with it. But what about all
those times we go back to our old backups and thankfully find what we
need?
That's true. It's not like 100% of all media rots to nothing. But
"finding" old media that's still readable is different from
"archiving".
I consistently read lots of data with nary a problem:
20-30 year old
floppy disks (5.25" and 8"), 20-30 year old mag tapes, even 20 year old
VHS tapes. And of course the punch cards don't count ;)
No offense, but you're in the business of doing so :-) Only a
minority of even us can read and convert old formats, even when
readable.
On Thu, 17 Mar 2005, Jim Leonard wrote:
If you somehow
think that tapes stored in a controlled vault is
more reliable, or less susceptible to bit rot than rotating
spindles, I believe you are wrong (and my every experience and
observation says otherwise). Only fiche and paper are statically
reliable.
You are omitting cost. Tapes in a vault cost significantly less over 10
years than the cost of 4 live systems + replacement hard drives + network
bandwidth + electricity for your method. Your method, unless I am misunderstanding you, has no
revisioning. It
protects against hardware failure, but how many revisions do you keep? What
protects against you mistakenly deleting the wrong directory, etc.?
That's what filesystems are for.
I also extended a rotating backup scheme I found on the net, that
uses hard links and an intentional feature of rsync; it fully
saves N copies of the data with true incremental changes with only
about 10% more diskspace than the original files themselves, for
data that changes at a "reasonable" rate of change (per week,
say). (Example: I have a big RAID server that has 5 weeks of 100%
snapshots; the original data is about 360GB, 5 weeks worth is
about 500GB.
http://wps.com/temp/rotate-backup
I agree completely that archival data should be
monitored in some fashion
instead of being locked away forever. And, cost permitting, transferred to
new media.
On rotating spindles, this is continuous...
On Thu, 17 Mar 2005, Dwight K. Elvey wrote:
One other thought is that one should have a way to
transfer the raw data from what ever media you have.
This allows one to have redundent information stored
on the same media. If you depend on normal file systems,
you run the risk of the file system not allowing you
to access the data simply because a small part is
damaged.
Hence multiple, ordinary servers, physically separate. The chances
of all of them developing a bad disk simultaneously is exceedingly
low.
If one of my servers craps a disk, that machine is repaired; data
from the other server(s) is automatically (cron) copied
to it.
Self-healing.
On Thu, 17 Mar 2005, Doc Shipley wrote:
>>> This reminds me that I read not too long
ago that many of the super
>>> computer labs ship PCs between sites because it's *faster* to ship a
>>> working PC with 1TB of disk containing data than it is to transfer it
Yikes, brings
new meaning to the term "Our System Crashed." Wonder
what the insurance is on something like that....
The insurance in that case was basically irrelevant. Their insurance would
cover the hardware replacement costs, period. Then the other issue was the archived files
themselves. Some of it was in
PageMaker, some in Wordstar, some in MS-DOS .prn files, and a lot of it in
AutoCAD r12 and a freeware DOS GIS tool whose name I've mercifully forgotten.
THen there's that! Added to the top of media recovery ("who's got
a 200bpi UNIVAC drive?") it generally means that the data is
simply "lost". (Few think to "SAVE-AS" plain ASCII for posterity;
I rarely do.)
I spent several hundred hours sorting backup sets,
restoring them to disk,
migrating files into current formats, and then archiving both current and
original copies to 4mm tape. It made for some very soothing afternoons,
hidden in my office.
And they only did it because it was required by law!
I'm seriously planning on printing out my website on paper. Laugh,
but it might be one of the few copies that survives long term.
That is, if I can find a printer that produces real output.
17 Mar
17 Mar
12:46 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
On Thu, 2005-03-17 at 00:32 -0800, Tom Jennings wrote:
Hard disk storage also neatly avoids the
incompatible-media issue;
it's continuously ported, incrementally. The translation issues
are from M to M+1, far less than trying to deal with 8" floppies,
1/2" tape or other once-standard media.
Also, for the moment at least, disks of tomorrow are chealer and
larger than disks of today, neatly taking care of increasing data
size (for how long this will hold out I don't know).
Whether you have 10MB or 1 TB of data, it's still cheaper with
rotating spindles. If you've really got a terabyte of data to
reliably save, backup tape isn't cheaper -- if you include the
longevity issue, of translating last-years tapes to next-years
tape. Who does that? Not many...
It's not about the medium, it's about the data. All of our mediums
suck for archival purposes, except paper and fiche.
Generally-speaking, our cultures don't directly care about
preserving the future, and machine media is a narrower case of
that.
This reminds me that I read not too long ago that many of the super
computer labs ship PCs between sites because it's *faster* to ship a
working PC with 1TB of disk containing data than it is to transfer it
over a long haul network (ie FedEx will get it there in ~24hrs...think
about the bandwidth required to transfer 1TB in ~24hrs). Not to mention
a whole lot cheaper! It also scales well!! :-)
Reminds me of the saying "Don't underestimate the bandwidth of a station
wagon full of tapes going at 60mph!".
(And yes, I probably got that quote wrong too!).
--
TTFN - Guy
9:42 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
Guy Sotomayor wrote:
On Thu, 2005-03-17 at 00:32 -0800, Tom Jennings wrote:
This reminds me that I read not too long ago that many of the super
computer labs ship PCs between sites because it's *faster* to ship a
working PC with 1TB of disk containing data than it is to transfer it
over a long haul network (ie FedEx will get it there in ~24hrs...think
about the bandwidth required to transfer 1TB in ~24hrs). Not to mention
a whole lot cheaper! It also scales well!! :-)
We have a client who owns what they call a "fleet" of SNAP servers
that rotate between San Antonio, TX, Delaware (I think), and California.
I haven't been involved with that contract in 3 years, but at that
time they had about 16TB on the road on any given weekday.
Doc
10:10 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
On Thu, 17 Mar 2005 11:42:30 -0600, Doc Shipley <doc at mdrconsult.com> wrote:
Guy Sotomayor wrote:
> On Thu, 2005-03-17 at 00:32 -0800, Tom Jennings wrote:
>
> This reminds me that I read not too long ago that many of the super
> computer labs ship PCs between sites because it's *faster* to ship a
> working PC with 1TB of disk containing data than it is to transfer it
We have a client who owns what they call a
"fleet" of SNAP servers
time they had about 16TB on the road on any given
weekday.
Yikes, brings new meaning to the term "Our System Crashed." Wonder
what the insurance is on something like that....
-dhbarr.
11:27 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
David H. Barr wrote:
On Thu, 17 Mar 2005 11:42:30 -0600, Doc Shipley
<doc at mdrconsult.com> wrote:
The insurance in that case was basically irrelevant. Their insurance
would cover the hardware replacement costs, period.
That same company looked at insuring 400TB of current data (maybe 15%
dynamic, but all of it needed online). The bottom line was that
assigning a meaningful value is not possible. Even in terms of lost
revenue, the formulae were, in Lloyd's of London's words, "necessarily
subjective and inconclusive".
Lloyd's were of course willing to insure against data loss anyway,
for any amount the client wanted to set on it, at about 1/3 that amount
per year. $client declined.
FWIW, I don't agree that it's not possible to maintain reliable data
backups. You can argue that they're never 100% foolproof, but nothing
ever is or will be.
My company does a lot of DRM and data protection (we're a Tivoli
sales, service & education partner). I get to see and hear how a lot of
shops handle their backups. Basically, it boils down to redundancy
(with geographic separation), versioning and revisioning, and
monitoring. Within sensible limits, the choice of media is entirely
optional.
Doc
>
>This reminds me that I read not too long ago that many of the super
>computer labs ship PCs between sites because it's *faster* to ship a
>working PC with 1TB of disk containing data than it is to transfer it
We have a client who owns what they call a
"fleet" of SNAP servers
time they had about 16TB on the road on any given
weekday.
Yikes, brings new meaning to the term "Our System Crashed." Wonder
what the insurance is on something like that.... 
8:08 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
Tom Jennings wrote:
I'd like to offer that there is no such thing as
archival computer
media. None.
This is not disputed.
If you somehow think that tapes stored in a controlled
vault is
more reliable, or less susceptible to bit rot than rotating
spindles, I believe you are wrong (and my every experience and
observation says otherwise). Only fiche and paper are statically
reliable.
You are omitting cost. Tapes in a vault cost significantly less over 10 years
than the cost of 4 live systems + replacement hard drives + network bandwidth +
electricity for your method.
Your method, unless I am misunderstanding you, has no revisioning. It protects
against hardware failure, but how many revisions do you keep? What protects
against you mistakenly deleting the wrong directory, etc.?
I agree completely that archival data should be monitored in some fashion
instead of being locked away forever. And, cost permitting, transferred to new
media.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Want to help an ambitious games project? http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
10:10 a.m.
New subject: archiving data, was RE: Media Longitevity/Care
Your method, unless I am misunderstanding you, has no
revisioning. It protects
against hardware failure, but how many revisions do you keep? What protects
against you mistakenly deleting the wrong directory, etc.?
Procedures.
The mainframe folks have been doing this for alost 40 years
(mostly) flawlessly.
William Donzelli
aw288 at osfn.org
12:26 p.m.
New subject: archiving data, was RE: Media Longitevity/Care
Jim Leonard wrote:
And, cost permitting,
transferred to new media.
As has been pointed out, that's rarely an issue in production
environments. Info gets migrated to new storage _formats_ long before
the current media's integrity comes into play.
Sometimes that migration can be interesting. When I went to work at
University of Texas, my department had a large file cabinet full of
archives. A lot of that dept's publications are funded by state and
federal money, so the research lab is required to archive all files and
information associated with subsidized publications for 40 years.
The first problem was that almost all their archives were on QIC-80
and QIC120, and the only tape drive in the building was a 4mm DDS drive.
I had to go over to Surplus and scrounge a floppy-interface Q120 drive.
Then I found that the first problem wasn't the main problem - nobody
in the building knew how those tapes were made. Fortunately the QIC120
drive was in a 486 system, and the Surplus guy wouldn't let me strip it,
so I ended up with the Jumbo software on its disk and that was what I
needed.
Then the other issue was the archived files themselves. Some of it
was in PageMaker, some in Wordstar, some in MS-DOS .prn files, and a lot
of it in AutoCAD r12 and a freeware DOS GIS tool whose name I've
mercifully forgotten.
I spent several hundred hours sorting backup sets, restoring them to
disk, migrating files into current formats, and then archiving both
current and original copies to 4mm tape. It made for some very soothing
afternoons, hidden in my office.
Doc
12:56 p.m.
New subject: archiving data, was RE: Media Longitevity/Care
Doc Shipley wrote:
Jim Leonard wrote:
Sorry, I implied new formats when I wrote "media" :-) My bad...
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Want to help an ambitious games project? http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
And, cost permitting, transferred to new media.
As has been pointed out, that's rarely an issue in production
environments. Info gets migrated to new storage _formats_ long before
the current media's integrity comes into play. 
1:42 p.m.
New subject: Slightly OT ceramic caps - not in DECs
This was p[osted on the Tekscopes bulletin board , I thought it may be of
interest here
Geoff.
Hello All,
Thanks to all that provided info on the 2221A. The problem was the
scope was totally dead. The failed part ended up being C945, a
0.1uF/50V monolithic cap that went to about 5 ohms resistance. This
appears to be a decoupling cap on the power supply inverter
transformer center-tap drive circuit. Very unusual that a ceramic
cap went bad instead of a tantalum or electrolytic.
Regards,
Jim
That is not quite as unusual for monolithic caps of that vintage. What you
are seeing is silver dendrite growth through cracks in ceramic. When cap is
abused, mechanically or thermally, the cap body (ceramic) cracks and in
presence of humidity and electrical field, silver (out of ink which forms
capacitor plates) leaches out along cracks and forms an irregular structure
that somewhat looks like a net and shorts the cap. Decoupling caps usually
clear up those shorts, but when not used often enough, or power supply folds
down at a relatively low currents (what is frequently a case on power up)
those shorts stay and just get beefed up over time. I have seen 50 A power
supply being held in fold-down mode by those dendrites.
In early 80s, when monolithic caps where new technology, they were accepted
quite enthusiastically because of higher capacitance density and low ESR,
both required for that new fungled thing called DRAM. Then came a rude
surprise, discovery that few months after assembly, mysterious shorts would
develop. Things looked so bad that there were even articles predicting that
monolithic caps would never make a viable product.
In days of through-the-hole components, radial and axial style monolithic
caps were usually encapsulated into a rectangular (cylindrical for axial
style) epoxy body, the same material as used for IC housing. The problem
with epoxy body was, and still is, that water, or rather water vapor,
penetrates along leads and supplies moisture for dendrite growth. To
mitigate epoxy's package lack of hermeticity, a new type of package was
introduced: glass encapsulated capacitor; that package was a variation on
the one used for diodes. It was very expensive, but some companies would pay
any price to get reliable decoupling cap; DEC was one of them. After around
mid 80s, all DEC CPU and memory boards used only glass encapsulated caps.
So do not be surprised that your cap failed, it happens all the time, less
frequently now then it used to be, but it still happens. The usual scenario
is that damaged caps form dendrites and when those caps are used as
decoupling (across power supply lines) shorts get cleared. After few
clearing iterations, there is no capacitance left, but no one is wiser, it
is decoupling; you just end up with a noisy board. However, if cap is used
on a signal line, usually there is not enough energy on such lines to clear
shorts, signals end up being shorted to some other signals or ground and
that is something that is not frequently suspected, so it is difficult to
find.
Regards
Miroslav Pokorni
7532
days inactive
7534
days old
15 comments
12 participants
participants (12)
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aw288＠osfn.org -
bv＠norbionics.com -
dhbarr＠gmail.com -
doc＠mdrconsult.com -
dwight.elvey＠amd.com -
geoffreythomas＠onetel.com -
ggs＠shiresoft.com -
mouse＠Rodents.Montreal.QC.CA -
tomj＠wps.com -
trixter＠oldskool.org -
vcf＠siconic.com -
willisjo＠zianet.com