To add a simplistic partial answer is that history (and research shows future tends) shows us that the two major requirements for having “forever”/persistent data is increasing at a rate that exceeds making this sustainable.
- data storage sizes
- unit drive storage is increasing at approx 10 times every 5 years
- unit production is increasing (at least doubling every 5 years and maybe much more)
- unit pricing dropping even through capacity is increasing
- basically what you stored 5 years ago on one drive will take 10% of a new drive
- basically what the world stored 5 years ago takes so much less than 5% of world’s storage now
- unit backbone links have been doubling in speed in approx 15-18 months for decades.
- Number of Backbone Links increasing year by year
- consumer links limited by political, commercial and user perception. Complex actions at play. Some homes in the world have 1Gbit/sec or higher links and some have 1Mbit/sec or lower links
- Basically bandwidth increases to meet demand.
From these two major factors determining the viability of “forever”/persistent data we can see in a simplistic fashion that it is quite viable to do.
So for a constant number of nodes what was stored 5 years ago will be taking much less than 5% of the current storage space for those nodes. When archive nodes (run by ordinary users) are added with permanent backup storage units the ability of the network to shift little used data to them comes available.
One other factor is that as the network grows so will the proportion of world’s storage move over to SAFE storage. So not only will data take up much less than 5% of space on a per node basis, with the network increasing year by year that data stored on SAFE 5 years ago will be taking a lot less than 5% of the current storage space on SAFE
As has been said, the rate of access to most older data decreases as time goes on and this means that bandwidth required for old data decreases. But this does not mean the value of that data decreases. Lost data or never used data is rendered impossible to detect because SAFE design makes it impossible for the even the network to know the data. To overcome this there may be introduced a way for the uploader to mark the chunk as temporary and then the network knows.
Finally something I didn’t see touched on is that we are now coming into the era where “Data is Valuable” This means that data in and of itself is valuable. Your family photos that are only stored on digital media, the last Will and Testament of your Father, the school results, and so on
A lot of this valuable data will only be accessed occasionally and to be kept Secure for a long time. This ability has to be open to Everyone. And SAFE will provide a safe way to store and Access this information without unwanted people getting access to it.
Basically a Secure Access For Everyone network