I’ve had bad experiences with CDs and DVDs being unreadable after a couple of years.
On the other hand, I have some really old hard drives, some of them IDE, more than 15 years old, and they are still readable.
Does it make sense reliability-wise to use an HDD as a long term storage, eg. write once and store for several years? Assuming good storage conditions (no heat, cold, light, humidity), will they become unreadable too if they are not used?
Reliability is low. Your 15 year drive could’ve easily been a 1 year drive. There’s a reason why there are HD check utilities, and bad sectors. I am not aware of any difference between IDE/PATA and SATA drives. SSD may be more reliable. If you’re that concerned, the appropriate RAID setup may be helpful, with replacements as needed.
CD/DVD media may be better in quality now, but yes, they too are crappy.
You can get gold-layered archive DVDs which, apparently, keep data intact for 100 years or so. They’re expensive, mind. I got my dad one (ONE) for Christmas (he’s a photographer), and it was £15.
I think it would be true to say that no-one really knows. The failure modes in HDDs are many and can be complex. There is a heck of a lot more to go wrong, and thus more ways it can. That and the problem that for the most part, HDDs have not been designed with long lifetimes as a goal, so many materials selections will have been made with a priority on storage density, performance, and price.
The failures I have seen over the years have run a gamut of issues. One failure was a bad batch of adhesive. When the disk warmed past a critical temperature the adhesive broke down, and centrifugal force caused it to spread over the disk surface. Another failure was stiction in the bearings - disk simply failed to spin up after it was turned off. Head crashes still occur due to contamination. Then you get failures in the electronics, head read amplifiers failing, controller failures, motor failures. Some failures leave the data intact, so that expensive recovery operations can get it back. Other failures are not so easily recoverable.
Long term, disks are probably the only viable way of archiving lots of data. But you want to archive with redundancy. Assume you will have failures. Every few years, read the data and archive it again on new media. Continual progress in media may make this cheap and easy, no matter how much data you have now. When you make redundant copies, don’t use the same brand or model HDD for each copy. Common design or manufacturing defects form a big part of failures.
Last time I had a dead hard drive, it was the act of copying from it that was damaging the drive, which meant I lost shitloads of data. Still very annoyed by that.
I wouldn’t count on even a well-stored hard drive to still be readable after a long hiatus. They are simply machines built out of necessity to very high tolerances, and there is quite a number of things that can affect them.
In general, you protect physical objects by putting them in a safe place, but you protect data by making lots and lots of copies.
That’s it right there. Redundancy is the only option.
if the data is valuable you want to back it up more than once.
sometimes HD can die slow and you can recover the data before death, but they also can die suddenly with costly (if at all) retrieval.
The biggest problem with the ever-larger drives is you are putting all your eggs in one basket.
If reliability is important, I suggest you invest in “enterprise class” drives, which are engineered to be stronger and less likely to fail. This may cost about $100 more per drive.
I have about 25 hard drives sitting around, from 750GB to 2TB, none more than 4 years old, and about 20% are bad, or at least not good enough to trust with valuable data. These are consumer-grade Seagate, Western Digital and Hitachi, and I don’t see much difference between them.
I have invested in two Drobos (NAS), which are designed for reliability and, using a proprietary RAID scheme, can protect against a single drive failure or, with more overhead, can handle a 2-drive failure and are hot-swappable. Tests have shown that the protection works, but it’s another case of all your eggs in one basket, for if the complete mechanism fails catastrophically, you’ve lost more than just one puny 4TB drive.
Still, I don’t see a better, long-term solution. Hard drives, as opposed to tape, are at least instantly online and the data randomly retrievable. DVDs and even Blu-Ray have an uncertain lifespan both technologically and physically, and are too small for the amount of data I need to store.
Anything has to be better than tape. I once attempted to retrieve some data on a company’s 10-year old tapes. About half the tapes had significant errors.
I use external hard drives for backups. In fact I just did my monthly backup of my home computers to a hard drive that I store at work. If the house burns down, I have photos and such stored safely elsewhere.
Still I wouldn’t want to depend on a mechanical device to work properly after sitting for a number of years.
I wonder if solid-state hard disks may be an answer? No moving parts. However they are expensive right now so may only be good for your most important data. Also I think they may need to be plugged in every once in a while to ‘refresh’ the data written on them.
As others have said, there’s a huge variability in hard drive life. I have in my box right now a 200GB drive that I’ve kept through several generations of upgrades–it still runs great. I’ve also had a 1TB drive that failed within a year. I make it a point to keep all my critical data backed up on multiple drives so no single drive failure will wipe it out.
This probably isn’t as dig of a deal as you think (note that the typical spec of 10 years applies at the maximum rated temperature, usually around 85C, and gets MUCH longer at room temperature; even going from 55C to 25C increases data retention time 18-fold), unless you are storing them for decades, but then you’d have problems with obsolescence (pretty sure that computers 10-20 years from now will be using something other than SATA as a drive interface, maybe even completely different file systems).
Incidentally, hard drives are far worse because you can’t refresh the data that tells the drive where the sectors are because the drive can’t actually write this by itself because it needs to read it in the first place to know where the heads are located (they use special equipment to write it down when they make the platters); this is why drives in otherwise good condition develop bad sectors and ultimately fail despite no damage to the platters or heads.
What about flash drives. Does anyone know how long they can hold data reliably? I’m thinking mainly of SSD’s here not usb thumb drives.