If a constraint was that it's going in a literal time capsule that would be buried underground (i.e. physical damage to the area is not controllable) I would get a couple of SSDs and a couple of backup tapes, and save redundant copies on different types of media. Given enough space I'd also stick a couple of machines capable of reading the data just in case.
Removing that constraint and completely ignoring cost I'd also setup a low-risk savings account with $1M in it and put the data on S3 and Rackspace Cloud. I'd store access credentials in the capsule. Odds are pretty good one of those 2 will be around in 50 years (and you'll have a chunk of money left over in interest).
Try to keep everything ASCII, with really good text descriptions of data formats.
Realistically 50 years is not a long time: I would bet we'll still have legacy access to USB, SATA, and probably ext3 & NTFS (though probably not IDE). Tons of computer folk who used these technologies will still be alive to work them. English will still be the primary language in the US.
An interesting problem is what to do when the timescale allows these things to change. What if nobody remembers USB, or what spinning platters are. Or the English language?
Neither tape nor SSDs will last 50 years. Within about 10 years, tapes will loose magnetization through thermal movement and capacitors in SSD storage cells will flip due to cosmic radiation. Over some decades the plastic the media and/or casings are made of will just decay (a serious problem for museums of modern art and design: http://www.getty.edu/conservation/science/plastics/index.htm...). The only media with a prooven track record of preservation over decades are acid free paper, parchment and non-organic materials like steel, stone and clay. But getting 5TB on an stone tablet has its very own challenges. [Edit: And using acid free paper won't buy you anything if you print using plastic based toner common in modern laser printers, at least use an inkjet with inorganic pigment (and not dye based) ink. If you look out for pitfalls like this, you might be able to implement your requirements with http://ronja.twibright.com/optar/ and only 125 metric tons of acid free paper, which you should be able to buy for less than $200000.]
Some people claim than MO media and DVD-RAM can guarantee 30 years, but this still is an estimate, they have not been around long enough to actually know.
The only "reliable" way to store digital data for more than five years known today is to copy them to new media well in advance of the old media loosing them, and even that is difficult if the amount of data is growing faster than the the storage technologies get faster. (I don't know if I should trust Eric Schmidt, but a few days ago he claimed that currently humanity generates as much data every two days as it did up until 2003, http://techcrunch.com/2010/08/04/schmidt-data )
People said floppy disks wouldn't last 30 years too. Yet, I've got some C64 disks that are approaching that age quickly. While I'm sure there is some corruption, most of them still work just fine.
If I was to store on magnetic media, I'd do it in a way that allows for some data loss (like usenet does with .par2 files). If you can stand to lose some of it, just pad it with enough redundancy for recovery and you'll be fine.
> People said floppy disks wouldn't last 30 years too. Yet, I've got some C64 disks that are approaching that age quickly. While I'm sure there is some corruption, most of them still work just fine.
I think that this is luck; I found a batch of 8-year-old floppies a few years ago, and more than 2/3 of them were unreadable.
I'd give a shot at DVD, make 3 copies of each disk, put the physical media in an air-tight container filled with helium, and put it all in a salt mine used for physical records storage.
You wouldn't need to use helium. Nitrogen is the standard "inert gas" for such purposes. At standard temperatures and pressures, N_2 does just as good a job at not reacting with stuff as noble gases do.
Just curious -- what is wrong with laser toner? It's carbon, and doesn't fade. And petroleum is "organic", but lasts for millions of years.
Edit: answered my own question. There are several kinds of toner (I had never heard of liquid toner), but some kinds are just fine:
"Toners composed of stable resin materials and a stable pigment such as carbon black are capable of strong bonding to the paper surface. Copies using these toners and printed onto permanent or archival quality paper can be considered permanent and suitable for long-term storage."
-- National Archives Australia
A SSD (flash-based) doesn't need to be powered. Finding a computer that has a SATA/IDE interface to read it back out after 50 years is an interesting problem, however.
[update]
Spansion quotes 20 years minimum. Under optimum conditions (whatever they may be) and with an adequate amount of redundancy, 50 years should be achievable.
Spansion single-bit-per-cell floating-gate flash devices are designed to provide 20 years of data retention after initial programming when exposed to a 125° C environment.
Spansion two-bit-per-cell MirrorBit flash devices are designed to provide 20 years of data retention after initial programming when exposed to an 85° C environment.
Both MirrorBit flash and floating gate flash are guaranteed to provide 20 years of data retention after initial programming when exposed to a 55° C environment. MirrorBit flash is guaranteed to retain data for up to the minimum guaranteed cycles (10,000). [F]loating gate is guaranteed to retain data after the guaranteed minimum of 100,000
cycles.
I've never heard of rechargeable batteries with a lifespan of 50 years. Also, the best quality photovoltaic solar cells have a lifespan of 25 years, and their output is down to around 5% of original capacity by the time 20 years rolls around.
Even better run a program on multiple servers that has the ability to move the data around different online storages and has the ability to seek out and buy more online storage solutions if required over time.
My answer to the last question would probably be including a reader right with it. AC current will likely be around a lot longer than 50 years. So if you have some kind of computer containing the data, just need to plug it in and it starts a self-explaining film(ideally with pictogrammes, several language explanations, etc) that should make the data usable...
Removing that constraint and completely ignoring cost I'd also setup a low-risk savings account with $1M in it and put the data on S3 and Rackspace Cloud. I'd store access credentials in the capsule. Odds are pretty good one of those 2 will be around in 50 years (and you'll have a chunk of money left over in interest).
Try to keep everything ASCII, with really good text descriptions of data formats.
Realistically 50 years is not a long time: I would bet we'll still have legacy access to USB, SATA, and probably ext3 & NTFS (though probably not IDE). Tons of computer folk who used these technologies will still be alive to work them. English will still be the primary language in the US.
An interesting problem is what to do when the timescale allows these things to change. What if nobody remembers USB, or what spinning platters are. Or the English language?