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https://www.xda-developers.com/your-unpowered-ssd-is-slowly-losing-your-data/
SSDs have all but replaced hard drives when it comes to primary storage. They're orders of magnitude faster, more convenient, and consume less power than mechanical hard drives. That said, if you're also using SSDs for cold storage, expecting the drives lying in your drawer to work perfectly after years, you might want to rethink your strategy. Your reliable SSD could suffer from corrupted or lost data if left unpowered for extended periods. This is why many users don't consider SSDs a reliable long-term storage medium, and prefer using hard drives, magnetic tape, or M-Disc instead.
Unlike hard drives that magnetize spinning discs to store data, SSDs modify the electrical charge in NAND flash cells to represent 0 and 1. NAND flash retains data in underlying transistors even when power is removed, similar to other forms of non-volatile memory. However, the duration for which your SSD can retain data without power is the key here. Even the cheapest SSDs, say those with QLC NAND, can safely store data for about a year of being completely unpowered. More expensive TLC NAND can retain data for up to 3 years, while MLC and SLC NAND are good for 5 years and 10 years of unpowered storage, respectively.
The problem is that most consumer SSDs use only TLC or QLC NAND, so users who leave their SSDs unpowered for over a year are risking the integrity of their data. The reliability of QLC NAND has improved over the years, so you should probably consider 2–3 years of unpowered usage as the guardrails. Without power, the voltage stored in the NAND cells can be lost, either resulting in missing data or completely useless drives.
This data retention deficiency of consumer SSDs makes them an unreliable medium for long-term data storage, especially for creative professionals and researchers. HDDs can suffer from bit rot, too, due to wear and tear, but they're still more resistant to power loss. If you haven't checked your archives in a while, I'd recommend doing so at the earliest.
(Score: 0) by Anonymous Coward on Monday December 01, @01:29AM (9 children)
I have a similar feeling about magnetic tape. I've heard stories about backup tapes that could only be read by the drive that wrote them...
Whereas HDDs come with the drive that wrote the data...
(Score: 0) by Anonymous Coward on Monday December 01, @08:08AM (2 children)
Nowadays basically all tape drives follow the LTO standards and are interoperable with other LTO drives of the same generation. But long-term compatibility is still a problem as the standards are updated every couple years and new drive models are not generally backwards compatible with old tapes (most generations could read one or two prior generations of tapes, but the latest LTO-10 is fully incompatible with all previous versions.
The people maintaining tape archives are presumably expected to switch to the latest formats as they become available and migrate all data which should be retained.
If you have a large tape archive and don't do this, you could end up like the BBC where they had something like a quarter million D-3 tapes as the only archival copies of things, and it was unknown if there were even enough working tape heads (which wear out over time) in the world to read them all.
(Score: 0) by Anonymous Coward on Monday December 01, @08:49AM (1 child)
Meanwhile I can easily use a SATA HDD from more than 10 years ago. So IMO if HDDs can do the job, it's better to use HDDs instead of tapes. Just store them well and don't drop them...
(Score: 2) by aafcac on Tuesday December 02, @04:15PM
HDDs aren't perfect, but they are cheap, reasonably durable, reasonably large and you can automate most of the process of verifying, repairing and transferring the data from one drive to a new drive as appropriate. We may someday get to the point where the interconnection is stable enough that that isn't needed, but we likely won't know that we're there until a rather long time after we hit that point. We may well be there with SATA as that hasn't been changing much in terms of wiring or chips other than more or less the same thing, but faster, but I'm not ready to make the assumption that we're not going to switch to something at some point. Especially with things like nVME chips being a common thing these days.
(Score: 2, Interesting) by pTamok on Monday December 01, @08:21AM (5 children)
> I've heard stories about backup tapes that could only be read by the drive that wrote them...
In the days of 9-track ½-inch tapes [wikipedia.org], that was a common occurrence as a result of head misalignment. I have war-stories about that, which I won't bore people with here.
(Score: 5, Interesting) by Unixnut on Monday December 01, @12:29PM (4 children)
I've had it happen with LTO tapes. Usually how it turns out is that a LTO drive falls out of misalignment (either due to age, lack of maintenance, or someone dropped it at some point and told nobody). The drive can write and read back its tapes absolutely fine, but if the drive fails and you switch it for another one, you find that all your tapes are unreadable.
Many moons ago this happened at a company I was a sysadmin at. We diligently did all the backups to LTO-3 tapes with verification step, marked them and put them in the offline storage vault for years. Then there was a disaster in the server room (it was in the basement, and a sewage pipe of the building burst flooding the basement. The smell was... indescribable) which took out all the servers and the LTO tape drive.
However when the dust settled and we were setting up the new server room, we found that the new LTO-3 drive could not read our tapes. Not a single tape of all the ones we had in the vault were readable. 3 years of monthly backups and not a single one could be read.
It was a major issue, in the end the company had to bring in a LTO specialist from the manufacturer who took one of our backup tapes, opened up the LTO drive and with an oscilloscope started deliberately misaligning the head until it could read our tapes.
It cost a huge amount in consulting fees but we got our data restored. Only saving grace was none of the IT team could be blamed, as all of us were hired within the three years, meaning if anyone had damaged the LTO drive, it was more than three years ago and were probably long gone.
A lesson in that you need at least two LTO drives, and you should verify on a different LTO drive to the one that wrote the tape, as the chance of both of them being misaligned in exactly the same way is infinitesimally small.
As for my personal back-ups. I use HDD's. I've managed to recover data off drives that were sitting in my attic for ~30 years (old Quantum fireball 4GB). It took a few taps to get the bearings to unstick and start spinning, but once up and spinning all the data was there, and I had no errors or access issues. In fact since then the drive spins up and works fine, just I can't find a use for it (seriously, I have USB keys that hold more data nowadays).
SSDs are good for daily high speed access, but I see no reason to not use the right technology for the job. For bulk and long term/archival storage HDD's and magnetic media work, Each has its niche.
(Score: 2, Insightful) by pTamok on Monday December 01, @02:22PM (3 children)
That sounds very, very similar to a couple of my war stories.
> you should verify on a different LTO drive to the one that wrote the tape
This is a/the key point. When verifying your backup, check also that it is readable in a different reader. Always.
(Score: 4, Interesting) by Unixnut on Monday December 01, @03:16PM (2 children)
No doubt, every war story I've heard follows a similar pattern. Usually involving prior bad decisions, lack of funding/interest from those in charge (who are not technically savvy) and an unfortunate disaster. I've been through a fair few of them. The "basements flooding" disaster were quite common, because back then the basement was the one place nobody wanted to work or be in but is a space which the company paid for, so logically it was the best place to put servers as they did not care about the smell or lack of natural light and thereby save money on office rental space.
The irony of the situation in my war story, is that after all that cost and rigmarole, the beancounters actually rejected our request to buy a second LTO drive, pointing out we now have a new one that has just been verified as "calibrated", so everything is now fine.
Back then I could not understand the short sightedness, but nowadays I have learned that there is a difference between capital and operational expenditure when it comes to tax write-offs and accounting, so perhaps it was the financially better off decision they made for the company.
Head misalignment is a common issue with devices where the recording medium is not always matched to the recording/playback equipment. I've had same issue above happen with my personal zip drives, and even with minidiscs.
It is also the reason I prefer to archive/backup on HDD's. The drive and heads are always aligned because they are built into the same enclosure. As long as I have an interface that can connect to the drive (currently SATA/SAS) I don't have to worry about misalignments, and so far the commonly mentioned failure modes of drives used for backups (e.g. stuck bearings) has not happened once.
Saying that, a lot of companies now just "back up to the cloud" so I don't think many even bother thinking about it anymore, but during the 2000's and before it was still an issue that many SME's had to think about. Probably why "Cloud" became so popular, as they didn't need to worry about this, or even need an IT employee anymore.
(Score: 2, Interesting) by pTamok on Monday December 01, @07:37PM (1 child)
Heh. Basement floodings are commonplace.
How about flooding an umpteenth floor data-centre in a high-rise office building*? That wasn't my story, but one I read. I thought it was in the The RISKS Forum Mailing List [seclists.org], but I wasn't able to find it the last time I searched for the source. There are some humdingers in that list.
As for 'backing up to the cloud', if your business relationship with the cloud provider fails, you lose access to the backups. This is generally not good for business. Similarly, there are various technical failures that can give you a really bad day. It's always DNS, unless it is a lost encryption key.
*Grundfos: Water distribution in high-rise buildings [grundfos.com]
Olympian Water Testing: Why do Tall Buildings have Water Towers on their Roofs? [olympianwatertesting.com]
(Score: 3, Interesting) by aafcac on Tuesday December 02, @04:22PM
I used to work security in a highrise where one of the standpipes storing water for the sprinklers had broken. That was before my time, but one of those systems can flood an area with an almost unimaginable amount of water in a matter of a few minutes if it breaks. But, a more common issue is for just one or a few of the sprinkler heads to start dumping water because they got triggered.
Water damage as you suggest is the biggest source of property damage in this context. Between plumbing disasters, literal floods and storm surges it's a lot.
My slightly off-site backups for the largest files I have go into a water resistant ammo can. It's not perfect, but if the sprinklers in the storage area do go off, it's good enough for that. If I were storing them there longer term, I'd probably throw a few desiccant packets in with the drive and use my vacuum sealer without the vacuum to seal it off. Which is fine, as that might be an issue in case of a fire, but if it's a fire hot enough to melt the vacuum seal plastic in a problematic way, it's likely hot enough to destroy the disk.