Tape Backup

[J. Clarke]

Thanks for the info. I actually thought that CD-R were permanent and
lasted forever, even if the plastic surface was scratched, while the
magnetic info on a HDD degraded eventually. What happens to the CD-R
after 3 months? Do they lose data?

3 months probably not, three years some do.

The upper surface of a CD is protected only by a layer of paint if that--if
it gets scratched the data is gone (people tend to be careful of the
bottom--if that gets scratched it can be polished, the top is the fragile
side). DVDs have a layer of plastic on top of the chemical and reflective
layers, so they're a good deal more durable in that regard, but I haven't
even seen claims of high longevity for them.

 

[J. Clarke]

I think that you are laboring under the misconception that bashing Travan,
which is crap, is semantically equivalent to bashing _tape_, which is a
useful storage medium.

I tend to agree!


Life of a 40 gigabyte disk: 5 or so years (even unpowered).

Seagate guarantees their drives for 5 years. They tend to last a lot longer
than that.

Life of a 20 gigabyte tape: more than that.

Life of a 20 gig DLT maybe, life of a 20 gig Travan I'd put in nanoseconds.
And DDS wear out in a year or so if regular backups are performed.

Failure mode of disk: frequently total.

If it fails at all it is usually total. So what?

Failure mode of tape: usually partial.

I've never had a "partial" failure of a Travan tape. When it's gone it's
_all_ gone.

One size doesn't fit all.

And tape has it's place.

Nobody said that _tape_ did not have it's place. VXA, DLT, LTO, even DDS
certainly have their place. So does Travan--it's place is in the landfill.

 

[Irwin]

Amazing. I always put CDs on the table with the label down, to protect
the bottom side. So, that is wrong? Amazing.

Irwin

 

[Al Dykes]

I tend to agree!


Life of a 40 gigabyte disk: 5 or so years (even unpowered).

Life of a 20 gigabyte tape: more than that.

Failure mode of disk: frequently total.

Failure mode of tape: usually partial.

One size doesn't fit all.

And tape has it's place.

Malc.

IMO you need two types of backup;

- one for your data. My Documents, for the sake of discussion.
- One for total disk failure

For the former, you need lots of generations, since you may want to go
back to an old verison of a document. For most of us a CDR (600MB) is
a good size. It's cheap and you can keep a pile of them. They can be
carried off site for disaster backup. This minimizes the chance of
data loss because a file on one of them degrades.

For the latter, most users just want the latest backup, a full image.
If the house burns down you have your data and documents off-site and
an off-site copy of your disk image is probably useless since the PC
you buy today will not run the image you made on your old PC. So
off-site is less important for the full image backup.

Images can be done disk-to-disk, fast. A second hard disk in a
machine will keep several generations of image backup, which is
important.

With this setup, it's unlikely that the image disk and the C drive
will die at once. If the C drive dies you buy another one at BestBuy
and you're back in busness in a few minutes. If the image disk dies
you buy another one, but all it has is backup images so you haven't
lost anything. Maxtor one-touch seems to be an idiot-proof solution to
image backups.

CDRs can degrade, and if your need old data you need to copy it to a
new generation of media every few years. And keep multiple copies,
and keep them in correct conditions. You also have to read back your
backups so you know the data is readable.

The US National Institute of Standards has a nice document on CD/DVD
media storage and lifetime.

http://www.itl.nist.gov/div895/carefordisc/

It turns out that one of the worst things you can do to a DVD is hold
it across the edges and flex it, as when you take it out of a movie
rental case. It can delaminate the layers.

 

[Arno Wagner]

Arno,

Why are CD-R and DVD+-R unreliable and short lived? I really don't
know.

My personal experience and that of people I know. The shortest CD-R life
I had so far was 5 minutes. It burned. It verified fine, 5 minutes later
the same drive could not read it. The problem is not so much that all
media are bad, but that quality and durability varies widely with no
way for the user to know which media are good and which are not. In
addition the burner/firmware/medium combination makes a huge difference.

You say HDD are reliable and medium life.

Medium = 5..20 years. The HDD manufacturers only state 5 year component
life. The problem is that there are components on HDDs (e.g. electrolyte
capacitors) that have a limited lifetime, even more so when unused.
Also part of the reliabaility claim is that you can suffer a complete
media loss if you drop them.

I have never dropped a
hard drive, but I have dropped a lot of backup CD-R, and I am guessing
that the CD-R tolerate physical abuse a lot better.

Yes: Mechanical on the underside. No: Scratches on the top, sunlight.

Now granted, I have
burned many a Drive Image CD, only to find that they don't verify
correctly. I never did understand where exactly the problem was in
that, was it software, burner, or medium?

All three (if you count the firmware of the drive as part of the software).

I guess that would qualify as
unreliable. It was be pretty devastating to try to restore a CD-R image
only to find that it was invalid and was your only backup. Actually, I
think that has happened to me before, I seem to remember. Is a
validated CD-R still unreliable and short-lived?

In my experience, that is unfortunately so.

I have some old HDD on a shelf in anti-static bags, and I don't
consider them particularly convenient. Also, how long does a HDD hold
data before it starts to corrupt?

Data corruption should take >>10 years. However HDDs for backups are
best done with the HDDs in removable drive bays or UDB/FireWire/SATA
external enclosures, which also protect the drive so some degree.

Arno

 

[Arno Wagner]

Thanks for the info. I actually thought that CD-R were permanent and
lasted forever, even if the plastic surface was scratched, while the
magnetic info on a HDD degraded eventually. What happens to the CD-R
after 3 months? Do they lose data?

Yes, we all have seen these manufacturer claims. The problem is chemical
degradation, often induces by light.

Example: A high-quality CD-R written exactly to manufacturer specification
and stored cool, dark and dry may actually keep 50 years or so,
but nobody really knows, the technology is still too new.
And there is a lot of variation and different chemicals used in
different media.
Also don't forget these are extremely cheap mass-market media.

Comparison: Any MOD (and a DVD-RAM in a cartridge, it is basically the
same technology) will keep >30 years when stored under normal
conditions. Some manufacturers today think that >80 years is
realistic, but for these long times accelerated ageing models
seem to be unreliable. In addition MOD (and DVD-RAM?) is
ISO-standardized. If it has the logo, then it has the
characteristics and the reliability.
These techologies are targetted at people that are willing to
pay more to actually keep their data.

 

[Arno Wagner]

I've never seen a reference to the magnetic domains degrading,
in the context of magnetic disk media.

It happens on floppy disk. It is pretty much a non-ussue on HDD,
since they a) keep longer b) other parts limit drive lifetime.

Arno

 

[Arno Wagner]

I've had numerous hard drives fail, resulting in any of data
corruption, specific sectors failing, or the whole drive failing. Any
serious backup system should include enough error
correction/redundancy to recover from sector and media failures.

That is why you do regular backups on at least 3 rotating media sets
(so you can go back to the backup one step older if the newest one
fails) and why you do a complete compare after the backup (so you
can identify problems with a medium early).

Still not extremely reliable. For that you should probably use
two different types of professional tapes at the same time,
put each backup and both media types and store the tapes in
different locations. However that costs far more than most
people are willing/able to pay.

Arno

 

[Arno Wagner]

Gee, this is terrible. According to the NIST thing, I am doing so many
things wrong. I write on them with a broad permanent marker which sure
smells like it uses solvents, sometimes with fine tip markers, and I
store the recorded media horizontally for years, sometimes in their own
cases laying down piled on top of each other, but usually just back in
the spindles they came in.

Funny thing, though, I have never, ever noticed a disc lose data it
once held. Could it all just be a lot of hype? Wouldn't be the first
time. So now I have to go back and try a few. Of course, figuring out
what was supposed to be on there and whether it is still good or not
won't be easy!

As said here before, if you have a good match between firmware, burner
and disk (and limit writing speed to 8x: personal observation for a
TEAC CD-E540E and Imation 40x CD-R) and store them in a dark place,
you can get years of data lifetime. There is just no way to predict
with which exact combination you will get this.

Wish me luck,

I do. You might need it.

Arno

 

[Arno Wagner]

High quality CDR (e.g. Mitsui Archive Gold) have undergone a lot of
testing and seem to be quite stable for long periods. The jury is
still out for DVDR. Hard drives contain all kinds of seals, filters,
lubricants on mechanical parts, and flash memory parameters and
firmware dependent on floating charges, all of which can decay over a
period of years. Hard drives are quite unreliable for long term
storage.

Indeed. The only good solutions for long-term storage is professional
tape intended for long-term storage (check the specs), MOD and (to a
lesser degree, since it is newer technology) DVD-RAM.

If you don't drop or overheat them, HDD reliability if fine for
regular backups. (Backup != long-term storage.)

I agree that DVD+/-R(W) is unclear at the moment. However the
German computer magazine c't does regular tests of burner/medium
combinations and has burned disks evaluated with professional
equipment. It does not look good. The same "speed before
reliability" marketing-driven philosophy that we know from CD-R
seems to be the current trend there.

Arno

 

[Arno Wagner]

You also need several generations of backup, and never overwrite your
best backup. (this applies to disks and re-writable media.)

Common consens here is 3 or more independent media sets in rotation.
If you keep backups for a longer time, add media sets. And be prepared
to have to restore from the second-newest set.

Unless you've actually tested a restore to bare iron you don't
know if your disaster recovery plan will work when you need it.

Not a media reliability issue, but very true! I had to do this once
(it worked), and since then I try this once a year or so with a spare
disk to be sure.

These days I do image backups to a pair of big disks in another
computer on my LAN, (these disks are synced in case one dies) and I
backup my data (mostly "My Documents") with some sync software that
keeps my laptop in sync with my desktop machine.

So-so from the point of reliability. Should be o.k.. Good for
convenience.

test test test .

And be sure what you actually test for!

Arno

 

[Al Dykes]

It happens on floppy disk. It is pretty much a non-ussue on HDD,
since they a) keep longer b) other parts limit drive lifetime.

Arno

Coercivity (measured in Oersteds) is the field strength necessary to
magnatize or demagnative magnetic media. A quick google shows that
floppy disks are at about 730 oersteds.
http://home.fujifilm.com/products/datamedia/fd.html

Hard disks are in the thousands.

ISTR that the earth's magnetic field is 1 oersted. (used to be called
1 gauss)

 

[Paul J. Hurley]

Has anyone here tried any of the online backup solutions offered by
some ISP's? Essentially you pay a monthly fee for a block of storage
(500MB, 1GB, 2GB, 5GB, whatever) on a server located "somewhere" and
some software that runs in the background on your local machine that
uploads files after changes, compressed and encrypted of course. The
advantage is that all of this is automated and there is no additional
hardware to deal with. This can be a disadvantage as well.

Opinions?

 

[Al Dykes]

Has anyone here tried any of the online backup solutions offered by
some ISP's? Essentially you pay a monthly fee for a block of storage
(500MB, 1GB, 2GB, 5GB, whatever) on a server located "somewhere" and
some software that runs in the background on your local machine that
uploads files after changes, compressed and encrypted of course. The
advantage is that all of this is automated and there is no additional
hardware to deal with. This can be a disadvantage as well.

Opinions?

I know people that have been using ibackup.com for several years
and I can recommend it. It's great for user data,
but it doesn't replace image backups for bare iron reinstalls
unless you are just writing MSWord docs and can sit down
on any PC with an internet connection to do your work.

It's "one touch backup", at least the way my friends
use it.

The access-your-data-anywhere is a nice feature.

You can get an ISP account with 500MB or more disk space
for a few bucks a months and use FTP to upload a ZIP
file of your documents.

For a business contigency plan, I'm sure that a responsible
online backup service has a EULA that should be read that lays
out terms and liabilities.

(no financial relationship with ibackup. I just see it used
on a daily basis.)

 

[Paul Rubin]

Has anyone here tried any of the online backup solutions offered by
some ISP's? Essentially you pay a monthly fee for a block of storage
(500MB, 1GB, 2GB, 5GB, whatever) on a server located "somewhere" and
some software that runs in the background on your local machine that
uploads files after changes, compressed and encrypted of course. The
advantage is that all of this is automated and there is no additional
hardware to deal with. This can be a disadvantage as well.

If it's just a few MB, that might work pretty well. Transferring 5GB
over a typical broadband connection will be pretty slow. Also, I
don't know any of those services that provide encryption on the client
side by default. You have to supply your own.

 

[Al Dykes]

If it's just a few MB, that might work pretty well. Transferring 5GB
over a typical broadband connection will be pretty slow. Also, I
don't know any of those services that provide encryption on the client
side by default. You have to supply your own.

The daily upload would be _really_ slow on an adsl line,
but some smart software that only sent modofied files would make
the best of things (or someting that works in background.

 

[Arno Wagner]

Has anyone here tried any of the online backup solutions offered by
some ISP's? Essentially you pay a monthly fee for a block of storage
(500MB, 1GB, 2GB, 5GB, whatever) on a server located "somewhere" and
some software that runs in the background on your local machine that
uploads files after changes, compressed and encrypted of course. The
advantage is that all of this is automated and there is no additional
hardware to deal with. This can be a disadvantage as well.

Opinions?

It is surely a good solution for a single off-site backup if
a) confidentiallity is really ensured
b) you data volume is low

It is not a replacement for a backup with several independent media
sets, unless the online service does that type of backup on the
storage, the cycle time fits your needs _and_ they allow you access
to older backups.

Arno

 

[Daniel Prince]

High reliability, high lifetime, medium cost, low capacity:
- MOD (3.5"), DVD-RAM

To long-term store lower volumes of critical (family photos,
diploma thesis, etc.) data use MOD or DVD-RAM.

Is that DVD-RAM in an original unopened cartridge only or would you
include DVD-RAM without a cartridge if it is handled carefully?

 

[Daniel Prince]

High reliability, high lifetime, medium cost, low capacity:
- MOD (3.5"), DVD-RAM

To long-term store lower volumes of critical (family photos,
diploma thesis, etc.) data use MOD or DVD-RAM.

Is that DVD-RAM in an original unopened cartridge only or would you
include DVD-RAM without a cartridge if it is handled carefully?

 

[Daniel Prince]

High reliability, high lifetime, medium cost, low capacity:
- MOD (3.5"), DVD-RAM

To long-term store lower volumes of critical (family photos,
diploma thesis, etc.) data use MOD or DVD-RAM.

Is that DVD-RAM in an original unopened cartridge only or would you
include DVD-RAM without a cartridge if it is handled carefully?