saving digital images

[genna_gurvich]

Hi everyone, my question is how to keep the gigabites of images saved

a long time without a fear to loose them. What is the best and

comfortable solution - hard drive, external hard drive, CDs, DVDs

or something alse, or combining several things?

I appreciat your participation at this forum.

[peter_white2]

Save them to a hard drive. Back up that hard drive to another hard drive.

 

Make sure that your copies get copied again every few years or so. That way the media the files reside on is never very old. The data itself can be very old, but as long as the media is in good condition, and as long as you can read the data, you should be all set.

[genna_gurvich]

Thank you Peter.

[Ed_Ingold]

CD's or DVD's are the best choice. You distribute the risk of damage or loss compared to hundreds of images on an hard drive. Hard drives are convenient, but hardly considered archival. The projected life of CD's and DVD's is 100 years or more.

[alice_guy]

"the projected life of CD's and DVD's is 100 years or more"

 

Edward,

 

Do you mind if I ask where you got this info from? I've heard less than substantial reports about the life epectancy of DVDs, mainly through a friend who is not allowed to use DVD as archival storage for medical records. He's been told that CDs are fairly stable but DVDs have a long way to go. Of course brands and materials vary so I'm sure there's no catch all answer. He may also (I'm hoping) have been misinformed.

 

Not wanting to start an arguement, just hopng to put my mind at rest with bona fide info to the contrary of what I've been told if it's out there somewhere.

 

Thanks in advance for any possible links or more info.

[Ed_Ingold]

Alice:

 

Estimates range from 30 years to over 100 years, depending on the substrate, handling and storage conditions (and, of course, the source). Your friend is subject to an executive decision. In my experience, managerial decisions of a technical nature are seldom based on science. Judge for yourself.

 

Two sources of interest are a white paper which can be downloaded from Memorex.com. The other is the publication "NIST Special Publication 500-252" regarding the storage and handling of optical media.

 

In 12 years, I have had no CD or DVD failure that cannot be attributed to mechanical damage or poor recording quality. In other words, most errors on optical media (in my experience) are generated at the time of writing. On the other hand, I have a catastrophic hard disk failure about every 18 months (I have over 20 active and swappable drives)

[mark u]

Maybe you haven't heard of the microbes that will eat CDs and DVDs?

 

http://www.informationweek.com/story/showArticle.jhtml?articleID=15800263&pgno=1

[godfrey]

What Peter said.

 

The key to digital archiving is replication and maintenance ... with digital image data, you

can make an infinite number of copies with no loss. If you make two/three copies and

migrate the data as media age and better media come about, 100% of the original data is

preserved forever (or as long as anyone cares to maintain it...).

 

I trust hard drives far more than I trust DVD and CD media for reliability, but longevity is

another matter. The reports on projected longevity of the optical media are a big question

mark as they are the result of stress testing and have little hard data in real long term

survivability to credit them. Optical media are combinations of dyes and metallic deposits

on plastic base material and it is obvious that these things do change over time, oxidize,

distort. However, that said, I've got CD-R media up to 10-11 years old that show no errors

and seem to work well still.

 

The solution is as I said at the beginning: replication. I archive my work to two hard drives,

which are mirror images of each other, and I archive important work to DVD and CD media

as well. Every couple of years or so, I buy another pair of drives that are double the

capacity (typically at half the price of the previous set), and copy all the data forward. Right

now I'm up to about 110G in the archive on 250G drives. When I hit 210G, I'll buy a pair of

500G drives... The old drives I used (80G models) are still good and are sitting on the shelf

storing the data up to their capacity too.

 

A couple of extra copies helps ensure that at least ONE copy will be available no matter

what happens.

 

Godfrey

[genna_gurvich]

A very interesting info. I also heard about two hard drives in mirror position. But it's a little to late for me. My 160G HD about 6 month old and doesn't want to be opened. the computer asks to formate the HD. My friend who is better in computers recomend to spend more then $700 to save the info on HD.

[jimstrutz]

There is no absolutely safe method, but the same is true of film, so this is not really a new problem. Digital has the advantage in being able to make multiple copies of original quality, storing them in different places, and refreshing them every few years. Multiple copies on multiple hard drives is probably the simplest solution. Backing this up with CD/DVD copies or another hard drives stored off site improves the security.

 

I also don't trust CD's for long term storage. Too many bad stories out there. The disc maufacturers don't agree on their reliability long term, and independent tests don't seem to agree with the maufacturers or each other. Who knows for sure?

 

The safest method has already been suggested and is to make redundant copies on different media, and recopy those every year or so, keeping at least one copy off site. It's simple, but not always easy.

[peter_white2]

The majority of the music CDs I bought twenty years ago have lots of little holes in the metal layer. Some of them no longer play, though most do. I've copied all of the ones that still work onto my computer hard drive with Apple I Tunes.

 

I'm not aware of any dramatic difference in disc technology that would convince me that today's DVD and CDROM discs will last all that much longer than the music discs I bought in 1986.

 

That's why I keep copying data while it's fairly fresh.

[peter_white2]

As Godfrey wrote, mirroring is good!

 

My server has two drives that each write exactly he same data. While using it, the computer appears to just have the one drive. But you look inside and there are two Seagate hard drives humming along. Get an Adaptec RAID controller and a second hard drive of the same model as what you already have. Once it's installed the controller will make an exact copy of what's already on your original hard drive to the second (new) hard drive. And from then on, whatever gets written will be written to both drives, without you having to do anything. You'll constantly have a full backup on that second drive.

 

If one drive fails, well, not if, but, WHEN one drive fails, the other will keep chugging along and you'll get a message on screen that you need to replace a hard drive. But you won't lose any data!

 

All hard drives will eventually fail. It's not a question of if it will fail. It's only a question of when. And you need to take the necessary steps to avoid data loss WHEN your hard drive fails. The only way to know for sure that you won't lose data when a drive fails is to have a real time backup. And a raid (Redundant Array of Identical Drives) controller is the best way to have a real time backup that I know of.

 

Raid controllers can also be used to speed things up, by writing half the data to one drive and half to the second. That's great but it doesn't give you the backup function. If you want to have the extra speed and the backup, you'll need to attach four drives; two to mirror, and two for the speed. But the Adaptec controller can handle all four drives if that's what you want to do. It's just the cost of the extra two drives.

[corey_gardner1]

Peter - which Adaptec controller do you recommend? There are several and the price is all over the board.