What about hard-drive-data shelf-life?
There's little data about 'shelf-life' in modern hard drives. Most reliability figures assume that the drive is in operation for at least part of the time. Simply storing a drive can cause its own type of breakdown - a very characteristic failure mode called 'stiction' was common on older drives which had been stored for several months (essentially, the lubricating oils could solidify once left undisturbed, eventually jamming the drive).
Depending on how important your data is I would be very careful in assuming that your drives will last longer than 5- 7 years.
If you need to store your data for a long time 5 years and up, you need to consider the ability to retrieve it from storage if required. E.g. my local hospital kept copies of CT and MRI scans on mageneto-optical disc since they first installed their scanners about 15 years ago. The original discs were 128 MB. Since then compatible, but higher performance, discs have been introduced, 500 MB, and lately 2 GB. However, a problem that has come to light in recent years is that even though all the discs and drives are from the same manufacturer and nominally compatible, the modern drives do not reliably read first generation discs. The hospital only has one working 1st generation drive left, which is sometimes the only way to read old discs.
While IDE and SATA are likely to be around for a long time to come, if you are planning on keeping drives for more than 10 years, you'd need to develop some sort of contingency plan in case SATA-IV (or whatever the technology of the day) controllers have some sort of compatability problem with older drives.
You may need to develop a policy of data 'refreshing' - where every 3-5 years you buy new state-of-the-art storage equipment and copy your entire archive onto the latest technology, ensuring that your data isn't stuck on obsolete and unusable technology.
I have to confess I do favour the use of optical storage with a very well supported format like DVD. I've never had a problem reading any medical CD on any computer even with 8 year old discs. The advantage of a ubiquitous format like DVD is that it's likely to be supported for a very long time into the future. Additionally, optical media has a very different set of failure modes to hard drives - so 2 archives, one optical, one HD could be complementary. If you do decide to implement an optical archive, make sure that you use 'archive grade' (or 'medical' grade) blanks. These are more expensive, but if your data storage needs are only about 0.5 TB a year, then this is unlikely to be much of an issue.
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