40 yearold computers still in use 91

Apologies for a tardy follow-up to this, but I thought some of these points worth picking up...

Mikko Nahkola

True to some extent. About 20 years ago I recall someone at our center doing a cost-benefit analysis looking at the storage of satellite weather images on film vs tape - we had both robotic tape libraries and high-res film recorders available to us. At the time, the film seemed to win out. Even though there were inevitable amounts of imprecision it was at a level comparable to or lower than the inherent errors in the original measurement. But the economics of that changed very shortly afterwards.

Lots of people have done and are continuing to do it, and doing research on how to do it more effectively. A quick google for "digital preservation" should get you some of them, including groups like the Digital Preservation Coalition. One of the things none of us are depending on is long-lived media. It simply makes more sense, and is much more cost-effective, to buttume that the media will not last more than a few years and plan to copy it frequently, and test it for accuracy and completeness even more frequently. Multiple copies are also indispensible. That deals with bitstream preservation, but not with the more complex problem of preserving the information, or some suitable rendering(s) of it.

Right now I don't think any of us believe there is one right way to do it, but some ways are more attractive, or can be seen to be more robust, than others. A lot depends on why you are keeping stuff and how often you expect it to be used.

One of the techniques is similar to something mentioned by Tony Epton further downthread. LOCKSS - Lots of Copies Keeps Stuff Safe - is a sort of distributed high-latency RAID. It deals well with the bitstream preservation but the other side of things requires quite a bit more work.

Kevin Ashley -- Kevin Ashley Digital Archives Dept ULCC