Halfbakery: Archiving Computer

So far as I know, the best way to store modern computer data for long-term purposes ("archival storage") is via "Magneto-Optical" or "MO" technology. It is based on a Natural phenomenon used by geophysicists, to read Earthly magnetic-field data that is hundreds of millions years old. That qualifies as superb "data retention" by any ordinary standard!

Basically MO technology starts with a "magnetically hard" substance that could be used to make a nice strong permanent magnet. This particular substance needs to be somewhat special, because it also needs optical properties that depend on the orientation of its magnetic field (I've linked an article below).

Anyway, all magnetic substances will lose their magnetism if the temperature rises enough (different for each substance, the particular temperature is called the "Curie Point"). In MO technolgy, a laser is used to heat a tiny spot on the data-disk, and a magnetic field can be applied to affect the orientation of that spot as it cools down and becomes magnetically hard again. (The Earth's magnetic field affects magnetic grains in cooling lava, and so geophysicists know the planet's magnetic field has flipped quite a few times during many millions of years.)

The optical properties of the cooled substance reflect a laser in different ways, depending on the way that spot has been magnetized (Kerr Effect).

For a number of years various manufacturers offered Magneto-Optical products. They are now being discontinued for several reasons. A few of those reasons are:
1. slow writing time compared to other products
2. competing products (like rewritable DVDs) arrived that hold more data
3. competing products arrived that have no mechanical parts (FLASH)

However, no other available technology appears to be matching the Long Term Data Retention possible with MO data storage. I'm linking a case in point, below.

Former MO manufacturers should seriously think about getting back into the business, specifically focusing on archival-storage products. Improvements such as blue lasers and perpendicular recording can be incorporated to increase data storage.

There is also a way to incorporate MO into a "normal" computer system such that the users seldom need to worry about slow write times. It might be possible to deliberately make a slower reader/writer, just to allow even more accurate and smaller and numerous data spots!

I'd also like to suggest a variant on "standard" MO disks that may be more quickly write-able. I'd still use a protective shell, to prevent scratches, but the disk itself would have a metal core (aluminum) and the MO substance would coat both sides. Inside the drive we would heat the whole disk (perhaps by magnetic induction)to a temperature a little below the Curie Point for the MO substance. Now the laser, instead of having to heat the spot on the disk from room temperature to the Curie Point, only needs to heat it a few degrees, taking a lot less time to write a spot of data. A drawback could be that the spot needs to COOL fairly quickly to freeze the data in place, which normally happens because a normal disk is mostly at room temperature. So, we can't heat the whole disk TOO close to the Curie Point, it needs to be far enough below that Point to allow fairly rapid cooling.

If that notion doesn't work out so well as I hope, then the don't-worry-how-slow-it-writes technique can still be done; it involves some help from the hardware and the Operating System, so I recommend getting the fast-responding Linux community involved in drivers and "default working pathways" and such.

Here is a description of some basic features of the Archiving Computer:
1. The regular hard disk drive should hold the OS and applications.
2. All data should be saved on the MO disk, but INDIRECTLY.
3. The system should be protected by an Uninterruptable Power Supply.
4. The system should incorporate a RAM disk the same capacity as the MO disk (say 8GB if the MO is 8GB).
5. The system UPS makes RAM disk cheaper than even the one I'm linking below (no backup power needed on-board, just I/O).
6. The RAM disk is be set up as an image of the MO disk.
7. Applications interact with the RAM disk faster than even a hard disk.
8. A background task can take its time copying new data to the MO disk. If smart enough, it might normally be able to avoid re-recording already-existing data, and could even automatically ensure files are defragmented, for faster reading later.
9. The MO disk reliably retains data for 40+years, possibly for thousands or millions of years if kept away from fire (no one knows for sure).
10. If the MO drive breaks, just replace it. The data is safe on individual disks. (This is another reason for manufacturers to get back into the business, maintaining stored-archive-retrieval technology.)