Question Magnetic Storage vs. Flash Storage

Feb 10, 2021
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I see that often people do come to forums to ask about practical solutions for their mundane problems and to obtain functional-based answers. Well, I'm here to ask about how storage hardware works on the electronics level.

First of all, how magnetic data storage differs from the flash one? How bunches of data are stored in a flash drive compared to a mechanical one? Why when you do turn off your PC, console or gadget the stored data doesn't degrade and "die"?

I've been working on the "surface" level of IT, understanding the operational factor of software/hardware but never questioned the basis of it all.

P.S.: English isn't my native language, so please consider it.
 

Karadjgne

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Storage, whether it's CD, DVD, Flash, magnetic all 'works' the same way. They read on/off binary machine language. It's in the 'how' they work that's entirely different. Cd/DVD etc passes light through minute holes in the substrate and reads those pulses as a on/off state. Hdds read the magnetic patterns, flash reads the stored ions charge. It all ends up as a bunch of 1's and 0's, which a cpu will render from machine to other languages.

Cd/DVD is the most permanent form, takes forever for that substrate to break down enough to deform the data stream. Unpowered SSDs are the least permanent, averaging 6 months to 1 year before the charges dissipate enough to corrupt the data. Hdds are somewhat up for grabs as the quality and age of the hdd affects just how long before magnetic bleed corrupts the data or sectors become magnetically worn out and will no longer hold data.
 
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hotaru.hino

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First of all, how magnetic data storage differs from the flash one? How bunches of data are stored in a flash drive compared to a mechanical one? Why when you do turn off your PC, console or gadget the stored data doesn't degrade and "die"?
For hard drives, this video sums it up pretty well:

For flash memory, the exact physics behind it gets a little complicated, but basically in flash media, memory cells are made up of transistors, which can store an electronic charge in a part of it. This charge provides a voltage and the value of the voltage determines what the binary value in the memory cell is. Flash media originally used only two voltage levels, but eventually started using four, then eight voltage levels. However, when resetting memory cells for reuse, not all of the charge goes away, so over time the charge starts building up. This is how flash memory has a limited amount of write cycles. Eventually the charge build-up gets so great that the device can no longer determine what the value is supposed to be.

EDIT: Also found a video that talks about flash memory
 
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Karadjgne

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Also, with a hdd, what you see is what you get. If it's 1Tb, it's 1Tb. With SSDs, that's not the case. A 1Tb ssd is in reality anywhere from 1Tb+7% to 1Tb+13% on average. That extra % is a redundancy factor that's used by TRIM. When a transistor builds up too much charge and becomes defunct, TRIM grabs a spare to fill its place out of the redundant stack. So while you'll see 100% life/health for a long time, it's really 113% or so that gradually works its way down to 100%, then to 99% after the redundant stack is depleted.

The better SSDs like Samsung tend towards the 113% range, the cheapo brands tend towards the 107% range. That redundant stack can seriously extend the usable life of the ssd, my 7 year old Samsung 840Pro just now hit 99%. Most hdds are basically good for 5 years, the better ones like WD Black can reach 7-8 years before serious consideration to replace before failure.
 

USAFRet

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Also, with a hdd, what you see is what you get. If it's 1Tb, it's 1Tb. With SSDs, that's not the case.
Actually, no.

A drive that is advertised as "1TB" on the box is reported by Windows as 931GB. That is HDD, SSD, a thumb drive, whatever.
It is simply a difference in reporting units. Base 2 vs Base 10.

There was even a lawsuit on this years ago, long before SSD's were a thing.
Now, there may be extra space on the die in an SSD, but that is irrelevant and invisible to the user.
1TB on the box is the same, HDD or SSD.
 

Karadjgne

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Well yeah, that's after windows is installed and hardware reserved and hiberfil.sys reserved and this and that reserved. Actual user usable space is the same, 1Tb. But when a HDD block fails its a permanent drop from 100% health to 99% health. Theres a finite limit and only goes down from there.
With the redundancy built into SSDs, damaged or burned out TX are replaced, the size of the drive doesn't change. You can lose upto @ 13% of it and Windows will still report the same '931Gb' usable, 1Tb 100% health. It's part of the reason larger SSDs last longer than smaller SSDs, larger redundant stack.
 

USAFRet

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Well yeah, that's after windows is installed and hardware reserved and hiberfil.sys reserved and this and that reserved. Actual user usable space is the same, 1Tb. But when a HDD block fails its a permanent drop from 100% health to 99% health. Theres a finite limit and only goes down from there.
With the redundancy built into SSDs, damaged or burned out TX are replaced, the size of the drive doesn't change. You can lose upto @ 13% of it and Windows will still report the same '931Gb' usable, 1Tb 100% health. It's part of the reason larger SSDs last longer than smaller SSDs, larger redundant stack.
Has nothing to do with Windows being installed and consuming space.

Again...Base 2 vs Base 10.
Computer vs Human
931GB = 1TB, be it SSD or HDD.

Yes, and SSD has additional cells behind the scenes.
Just like an HDD has sectors that are available for remapping of bad sectors.
Those are irrelevant, in the eyes of the user and what is printed on the box.

A 1TB Samsung 860 EVO reads exactly the same as a 1TB WD Blue spinner.

https://docs.ukcloud.com/articles/other/other-ref-gib.html
https://www.gbmb.org/gib-to-gb

(from 2007) https://www.cnet.com/news/gigabytes-vs-gibibytes-class-action-suit-nears-end/
 

Karadjgne

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You are talking about actual numbered physical size, I wasn't. And I've never heard of a hdd having extra redundant sectors that get remapped to replace bad sectors, although that would make sense in the server use discs. I've always known bad sectors to get flagged and those physical addresses to be taken out of use, no longer usable, basically non-existant. It's a spinning disc, the only thing that the head can do is physically skip over that bad sector that's permanently stuck exactly where ever it is. Ssd has no physical 'place' to skip, addressing is virtual not physical in that sense.

Meaning if a Samsung 860 Evo 1Tb looses 13% of its 'sectors' it's still a 1Tb to start with.

A WD Blue spinner loses 13% of its sectors, it's no longer 1Tb, it's 870Gb. No physical replacement
 

USAFRet

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Karadjgne

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Learn something new every day. I went through that phase of having to allocate bad sectors manually, that sucked. Got used to Defrag and CHKDSK doin it all for me after that. So this sector pool is something new to me, it's the first I've ever heard of it. Although I guess its old for others ppl.

Thank you. 😁
 

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