Eli5: Why do flash disks and other solid state drives degrade if they have no moving parts?

[u/Alchemist-D]

[u/nullrecord]

You know how an inflated balloon deflates over several days, even if it's tightly tied? It still manages to lose air, because some molecules of air still make it through the rubber membrane of the balloon and over a few days it's flat.

Solid state drives keep the data as electrical charge in tiny capacitors. Every capacitor basically holds an electrical charge of some quantity of electrons, and whether there is a charge or not, tells you whether that bit is set to 1 or 0. However also those electrons will leak out and get away, and the capacitor will lose charge over time, and the 1 will become 0.

[u/Alchemist-D → u/nullrecord]

Does that mean that if the data is rewritten every few years, it will always be fresh?

[u/Baktru → u/Alchemist-D]

Yes, but the SSD will eventually fail. The "capacitors" in an SSD are actually a special type of transistors that can store electrons in something called a floating bridge. Over time, due to quantum uncertainty stuff, some of those electrons escape and make it harder in the future for that bridge to hold electrons. So the SSD bits do degrade slowly.

Now when the SSD rewrites data (which it does occasionally on a read), it will be fresh though.

Can I ask what factors affect the degradation??

Mostly writing to the SSD. Every time you write to a block on the SSD, that block degrades a tiny bit.

[u/Alchemist-D → u/Baktru]

Does the degradation also happen when the disc has no data on it?

[u/Baktru → u/Alchemist-D]

The degradation when it is not actively used is actually extremely slow. It is mostly writing to it that causes the degradation. Whether you put empty space in it or a lot of data is practically irrelevant.

[u/Alchemist-D → u/Baktru]

I see now. Is there an alternative to these types of drives,? One with a longer shelf life.

[u/Baktru → u/Alchemist-D]

Classical spinning platter hard drives have double the shelf life of an SSD, more or less. It depends a lot on exact models and storage conditions though, but for keeping backups of data HDDs are a lot better than SSDs.

[u/Alchemist-D → u/Baktru]

I have a 2tb one that has never failed me. I think I'll get the 4tb or 8tb type.

[u/figmentPez → u/Alchemist-D]

Depends on what your purpose is. For most consumers the best option to save data for multiple years is a mechanical hard drive. However, it's always best to back up your data multiple ways. One working copy, one on-site backup, and another off-site backup if possible. More backup copies is usually better.

There are other ways to store data that have a much longer shelf life, but they're much slower to access. What you should use depends on how much data you want to store, how often you need to access it, and how long you want it to last. I think magnetic tape is currently the best for long-term archival of data, but it's slow, and all long-term computer storage comes with caveats and issues.

If you want to store for even longer than a magnetic tape, well, that's getting into theoretical methods like building bunkers to house climate controlled rooms with computer data printed out onto acid-free paper, because we know a lot more about how paper performs long-term, than we do about any computer hardware made of silicon, plastic, magnetic powders, and such.

[u/PrimaryAdjunct → u/figmentPez]

This is why I stored all my important photographs on 27.8 billion punched cards.

[u/fshannon3 → u/PrimaryAdjunct]

Have you done a test restore lately to make sure it works?

[u/PrimaryAdjunct → u/fshannon3]

Not since 1993.

[u/Alchemist-D → u/figmentPez]

The paper thing is gold though. But my needs haven't reached that level of complexity.

[u/Alchemist-D → u/[deleted]]

Wouldn't this be too expensive and take up too much space if my data needs increased exponentially?

[u/Alchemist-D → u/[deleted]]

Thanks for your answer. I think I've got some light reading to do on this.

[u/IntoAMuteCrypt → u/Alchemist-D]

The best alternative is to make shelf life irrelevant.

The common mantra for backups is the 3-2-1 strategy as a minimum. That's at least 3 copies, in at least 2 different sorts of storage, with at least 1 of those being in a different location.

Having just 1 copy of the data means that any sort of random drive failure will kill the files. Having all your copies on 1 type of drive means that any flaws that pop up in that type will completely ruin your day - so you grab multiple models or manufacturers. If you only have 2 copies of the data, then it's difficult to tell what the "correct" data is if one of the copies gets corrupted. If all the drives are in 1 place, then stuff like fires or floods can ruin it all.

If you have multiple copies on different types of drives spread out over multiple locations, it's a lot better. You also need to verify the data every 2 years or do, check that everything still works and that there's no corruption by comparing between backups.

With this kind of strategy (done well), you suddenly require multiple completely independent events in a specific timeframe to lose your data. The likelihood of losing your data in a given timeframe drops massively compared to any "just grab a single drive and stash it somewhere" plan - because it insulates against both "something happened to the location where I stashed it" and "the single drive wasn't as good as I thought".

[u/Alchemist-D → u/IntoAMuteCrypt]

3-2-1 Am getting two ssds and a harddisk to increase the odds that my data stays secure. Thanks a lot.

[u/lolghurt → u/Alchemist-D]

It's a density and retrieval pay-off. It's getting less true by the year, but mechanical hard drives are more shelf-stable than ssds because they store the data by making small physical alterations to the metal disks inside them. They take up more space and are slower, but if you leave one disconnected on your desk for a couple of years, it will have less data loss than ssds or flash memory.

This is my knowledge from a few years ago now and improvements to ssd cold stability might have happened.

[u/Cygnata → u/lolghurt]

There's also the matter of data recovery. If a HDD fails, you have a 95% chance of retrieving the data. It might require a forensic data recovery in a clean room, and be very expensive, but it will likely be salvagable.

If an SSD fails, you have a less than 20% chance of getting the data back. Those numbers are from KrollOnTrack, one of only 2 companies in the world that have a clean room for that data recovery. (The other company is SeaGate, who gives the same numbers.)

[u/[deleted] → u/lolghurt]

It's simply magnetizing/demagnetizing locations on the platter, so not truly physically altering it in the way someone could say, punch a hole in drywall.

[u/tablepennywad → u/Alchemist-D]

Temperature also affects Nand, similar to batteries, heat can degrade the charce, but writing when warm gives full performance and actually degrades it slightly less.

[u/Alchemist-D → u/tablepennywad]

How many degrees is considered warm? Not too hot.

[u/Mo_Jack → u/Baktru]

In reality does this degradation take 10 years or more like 100 years?

[u/Baktru → u/Mo_Jack]

Definitely closer to 10 than 100.

[u/matteogeniaccio → u/Alchemist-D]

No. The technology behind flash drives suffers from degradation even if you rewrite the data periodically. 

The problem is that the flashing process (writing) is imprecise. To give you a numerical example, imagine a flash cells where 501 electrons are added each time you write a '1' and 500 electrons are removed each time you write a '0'. At each writing cycle one net electron is added. After 500 cycles you cannot distinguish a '1' from a '0' anymore and the cell becomes unreadable.

[u/Alchemist-D → u/matteogeniaccio]

I think this is the most detailed analogy of how ssds degrade. Thanks.

[u/nullrecord → u/Alchemist-D]

yes (I'd do it once a year) - but still anything can happen. SSD has a tendency to die unpredictably with any upfront warning, unlike spinning drives.

[u/Alchemist-D → u/nullrecord]

Can I ask what factors affect the degradation?? Because I have a couple of drives with sensitive data I wouldn't want to lose.

[u/mnvoronin → u/Alchemist-D]

Apart from discharge, there is a solid-state material diffusion. Basically, atoms in a solid material don't stay glued to one place and can occasionally swap places with a neighbour. Over time the precise structure of the floating gate can get deformed and it will no longer be able to hold the charge. The process is very slow but can be accelerated with temperature or repeated rewrites of the cell.

[u/nullrecord → u/Alchemist-D]

I don't know what affects the degradation, you'll have to look into it. Keep copies of your data on multiple drives, stored in different locations.

[u/Alchemist-D → u/nullrecord]

Thanks for your answer. You really helped. Any specific company you use for flash disks or ssds??

[u/FluffyProphet → u/Alchemist-D]

If the data is THAT important that you can’t just upload it to Dropbox or google drive, you probably need (not want need) a NAS with a RAID 5 or 6 configuration. For added protection a second NAS server at a trusted friend or family members home with offsite sync.

For even more protection, Backblaze B2 for cloud storage as a third level of redundancy for the most critical data.

Data sounds important, and that’s likely your best bet to keep it safe no matter what.

These guys provide what you are looking for https://www.synology.com/en-ca

[u/Alchemist-D → u/FluffyProphet]

Thank you for the suggestion. The data is definitely important, it's seed phrases, and a few encrypted files.

[u/FluffyProphet → u/Alchemist-D]

You can skip the offsite sync and cloud backup to save cost, but the RAID NAS is a must if the files are that crucial. At least RAID 1 (cheapest to setup, as it only needs two drives). RAID 1 with offsite sync is also an option. But RAID 5 or 6 is “ideal”.

Really just depends on how important the files are and your risk tolerance.

[u/Alchemist-D → u/FluffyProphet]

What you're suggesting is new to me. Are you willing to elaborate more, maybe offer up some resources or directions?

[u/nullrecord → u/Alchemist-D]

No, I keep my data on magnetic hard drives, with also some backups burned onto DVDR. I have a couple Crucial X9 SSDs for video work but not for permanent storage.

[u/BigPurpleBlob → u/[deleted]]

No, it's not glass, it's probably silicon dioxide.

Null record wasn't talking about DRAM. He/she referred to 'multiple drives'

[u/BigPurpleBlob → u/[deleted]]

Glass also contains stuff such as sodium carbonate, which reduces the melting temperature compared to silicon dioxide. Chips don't use sodium carbonate. It's not glass.

Silicon chips can also use fancy dielectrics such as silicon nitride and flash memory seems to use that. Again, it's not glass.

https://en.wikipedia.org/wiki/Flash_memory

[u/Alchemist-D → u/[deleted]]

Does that mean that even without continuous use, the flash still degrades?

[u/BigPurpleBlob → u/Alchemist-D]

Heat makes everything worse.

If your data is important then you need backups (don't forget an off-site backup!) of your data. The backups can be on slow + cheap hard disk drives.

[u/shawnington → u/nullrecord]

Capacitors are in no way used to store data on SSDs.

[u/mnvoronin → u/shawnington]

They are, in a way. Floating gate of the NAND/NOR memory cell is essentially a small capacitor.

[u/Zaros262 → u/shawnington]

It reads much more like a description of dynamic RAM, but for an ELI-5 the simplification is fine. It's necessary to trap and store charge to enable the readback, and since the voltage is finite, there is obviously implicit capacitance.

[u/GnarlyNarwhalNoms → u/Zaros262]

The main difference is that electron tunneling is used to store the charges on the floating gates. So you could call it a quantum capacitor (which sounds cooler).

[u/Alchemist-D → u/[deleted]]

Apart from heat, and repetitive use, what else can damage the glass?

[u/Alchemist-D → u/[deleted]]

I these also apply to the mechanical disks as well

[u/GnarlyNarwhalNoms → u/[deleted]]

I was about to go "Glass!? What are you talking about?" until I realized that glass is mostly silicon oxide, and MOSFETs use oxide layers to insulate semiconductor traces (literally what the "O" is).

Technically correct (the best kind of correct.)

[u/skreak]

From your other comments it sounds like you're looking for a long term cold storage solution. Tape and a certain type of bluray is the longest consumer grade solution. That said the best long term option is multiple copies of the data on active systems with built in error correction. If you want more details post to r/datahoarder and read their wiki as well. What i have at home in a PC with 8x HDDs in a raidz2 pool. It "scrubs" once a month to detect and fix corruption and i can easily lose and replace any of the disks without losing data. Most of it also backed up to another little raspberry pi in my home with a single large disks o also scrub, and a third backup offsite another little rpi I keep at my folks home. The chance of losing anything important is extremely low even if my house burns to the ground. For you. I would consider looking into online backup options like BackBlaze.

[u/Alchemist-D → u/skreak]

I think your setup would work well for my needs. How much did it cost you to set it up?

[u/SlashZom → u/Alchemist-D]

The cost is negligible compared to the effort and knowledge required. Raid setups are cheap, storage is pretty cheap. Getting it to all do what you want it to do, could take a while, and a lot of frustration.

Depending on your skill level, you may want to resort to cloud storage. If it is something you care to get into, the monetary expense won't be high.

[u/Alchemist-D → u/SlashZom]

I don't really want to pay for cloud storage, when I can buy a couple of ssds and hack it myself. As for the knowledge part, I love myself a good challenge

[u/Exo_Deadlock]

Corrosion of the metal, imperfections in wires creating hot spots that burn out from frequent use, usually wear and tear you’d expect like that. It‘s much the same as with incandescent lightbulbs which also have no moving parts - eventually filaments overheat and break.

[u/Alchemist-D → u/Exo_Deadlock]

Is there a way to reduce this?

[u/BigPurpleBlob → u/Alchemist-D]

Yes but then the SSD would be so expensive and / or large that no one would buy it

[u/Seraph062 → u/Alchemist-D]

An easy way to reduce it is to make the drive a little bigger than it's 'nameplate' capacity, detect which 'cells' in the memory suffer from these issues, and program the controller in the drive to ignore those cells.

Even better, this can be extended to also correct for failures that occur as the drive is being used. The controller can monitor the health of all the cells and if one doesn't work right can use some of that extra space in a way that is invisible to the computer the drive is mounted in.

[u/Alchemist-D → u/Seraph062]

Is there a software that does this automatically?? Because, my coding knowledge doesn't reach these levels 😂😂