Hi!
What’s the difference between an external HDD and an external SSD? I know SSDs are faster, but are they actually better for long-term file storage? I’ve read that they might not be ideal, since if an SSD isn’t powered on once in a while, the data can eventually get corrupted or lost.
What would you recommend for reliable long-term storage?
Both HDD and SSDs are fine for cold storage.
There is a myth that SSDs have worse data retention, however the only conclusive studies made were made in 2010 on drives that had reached End-Of-Life. So unless your drive is bought second hand from something that wrote hundreds of GB every day for years to said drive, well…
And even in that case, powering on the drive once every 18 months or so for one hour should be enough to regenerate all cells in the drive. And SSD technology has only improved the last 15 years.
So yeah, these days the only difference is how much time you are willing to wait to fill up a 24TB HDD, pretty much. I welcome any recent data that isn’t pure anecdotal though.
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I would say that hdd´s are probably still a bit more reliable when it comes to longer,
and larger file storage compared to a ssd.
However in regards to ssd´s it also highly depends on which type of ssd´s you use.
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LTO7 Tape and a bank safety deposit box.
Yes, i count this as my offsite backup.
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This thread is a good read on the current situation SSDs find themselves in WRT data retention:
TLDR: almost all consumer SSDs, even if periodically powered on, will let data degrade over time; the degradation mostly affects the read speed of the data and it isn’t until years later that’d you’d have to worry about the data actually being corrupted (this is assuming the SSD still has reasonable health of course).
As long as nothing goes wrong mechanically with HDDs, I’d expect them to retain data for multiple decades; I’d preclude EAMR HDDs from this statement until they prove their long term reliability alittle more however.
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My NAS is made of old HDDs that still say Hitachi. And i abuse the array. Not a single issue with any of those drives. This array has been under abusive workload for about 7 years now. Hitachi seems to have built their HDDs to last.
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I’m a big fan of HGST drives, I’ve got some 4TB units that have been running for more than a decade and no failures (although they’ve mostly been used for archival rather than anything too stressful).
When Western Digital swallowed them up it didn’t seem like much of the reliability Hitachi was know for was absorbed into them.
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That’s how hardware should be. HGST certainly remains a quality brand even today. But in 2025 I have a hard time justifying 5W of power for just 4TB. TB/W slowly makes those old drives uneconomical. A shame to replace good and running drives. And in the time before SSDs, where ever HDD was contributing to the overall IOPS, even old drives had their place. HDDs are pure capacity to me now.
Back to topic:
Neither is considered to be good for long-term storage. SSD loses charges over time, HDDs and magnetization isn’t that trustworthy when 7+ yrs of being offline in some basement box is the task.
I would recommend, if using SSDs and HDDs for that, to plug them in every 2-3 years (SSDs maybe shorter intervals, not sure) and do a scrub and/or full disk rewrite. Dusting them off so to say and put them back afterwards.
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I remember when I started my career in early 2000s. What is now HGST were known as IBM DeathStars back then… 
Great that they are more reliable now though!
I lost a good portion of data due to corruption on a Samsung 970 EVO that was no where near its end of life, it was barely used, and the data had only been sitting cold for around 18 months.
Similar thing happened on an Intel SSD years before, but the drive was around the middle of its life and sat for longer so I didnt really think much of it.
But now I would never trust any data on NAND for cold storage, and really not even hot long term storage unless it is an enterprise drive.
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This is anecdotal, but some of the SSD manufactures that cater to the extreme reliability market explicitly state that they NOR flash instead of NAND flash for very important things like drive firmware:
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oblig:
no media retains data long term
make sure you have multiple copies in multiple locations
also check they work periodically, and refresh the media as applicable.
expecting 10 year old media of ANY type to be reliable is a fools errand. well, maybe millennium disc might be ok. but i still wouldn’t just blindly trust it, and i certainly wouldn’t trust only one of them to not be lost/destroyed/stolen/etc.
edit:
well, technically carving your shit into stone tablets Egyptian pharaoh style is technically media, and has been demonstrated to last thousands of years but i doubt you’re doing that at scale.
I’ve seen / dealt with enough broken LTO tapes that i would not rely on this as a single source either.
I’ve also personally had multiple LTO tape libraries destroy tapes so… yeah…
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If long-term storage is what you’re after and you don’t have a set budget you should look into tape drives.
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This. If you’re doing LTO tape backups, always do more than one tape copy.
I always do two copies and store one of them in friend’s house in case my copy goes bad
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Thanks for sharing your experience! After reading this, I’ve decided to go with an HDD.
And I’ll make a backup, as a precaution.
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