SSDs have a valuable place in the world, but so do spinning disks. Physical size isn't a concern for my nas (I mean, assuming we're talking < 300cm^3 for the whole setup..), but $/tb is.
There was literally a headline on the front page here a few days ago re: data degradation of SSDs during cold storage, as one example.
Why is that? I'd have expected solid-state electronics to last longer at low temperatures.
Or is it precisely that, some near/superconductivity effects causing naughty electrons to escape and wander about?
High capacity hard drives nowadays use heat and strong magnetic fields to write patterns into the platter. It's pretty stable just sitting around doing nothing.
High density multi level NAND involves quantum tunneling a few electrons using a strong electric field into an electrically insulated bit of semiconductor. Over some time the electrons tunnel their way out, but usually this only ends up actually happening if too much writing damaged the insulation.
Or does the data decay there as well, just as a function of time since cells were written?
In other words, is this whole focus on "powered off" just a proxy for "written once" versus "live data with presumed turnover"? Or do the cells really age more rapidly without power?
If you are paranoid about your data and not relying on filesystem level checks from ZFS or Btrfs you should ptobably avoid SSDs for long term storage.
There are "hardware level checks", it's just that they might assume regular usage. If your SSD is turned on regularly (eg. a few hours a day at least), your files are probably fine, even if you never read/scrub your rarely read files. If it is infrequently used, you're right that you probably have to do an end-to-end scan to make sure everything gets checked and possibly re-written.
SSD also has longer term data loss issues when unpowered. Magnetic disk is still better in that respect too.
There are still deals to be found that are closish.
Microcenter has a 24tb external for $249 right now: https://www.microcenter.com/product/679395/seagate-24tb-expa...
amazon has a 22tb for $229 right now: https://www.amazon.com/Seagate-Expansion-22TB-External-Drive...
Those and my $189 price - which is definitely higher than I originally claimed, apologies - are all around $10/tb.
See the 20TB+ Seagate external drives. People who just want the 3.5" SATA drives remove them from the plastic enclosure (they call it "shucking").
External Storage 26TB for $10.38/TB - Seagate Drive Internal Storage 24TB for $10.81/TB - Seagate Drive
SSD - $48.75 / TB Crucial !
Isn't 0.1TB a little too low? I'm sure if they only improved this little in 5 years the company would be in big trouble.
these 6.9TB platters are still in development and are not planned to be used for another 5 years.
Western Digital would like to have a word about shingled magnetic recording drives.
https://www.tomshardware.com/pc-components/hdds/wd-launches-...
Doesn't matter if your use case is only stashing porn, mine is stashing archived web pages and wikis, for example. So integrity of both the HDD sectors and filesystem sectors really matters to me.
I also wanted to make a point about regulation requirements. If you cannot guarantee integrity of your backups, all compliance gets thrown out of the window, and your company will be closed if that info gets out.
This requirement is also the case for private citizens when it comes to preservations of filed bills and taxes, for the last 10 years, in all EU countries.
The ideal has been achieved. We need go no further.
So very roughly, about 1 bit per square nanometre. Which unless I'm dropping an order of magnitude (very possible) is about 10 petabits per square centimetre, and with about 300 square centimetres for a 3.5" platter that's 3 exabits or so per side of platter.
Whether it will ever be possible to actually read or magnetize domains that small without interfering with the neighbouring domains is the question and no one knows. There have been several breakthroughs, like perpendicular recording, that have brought us much closer to the theoretical limit above, than anyone would have thought.
Neywiny•2mo ago
Wow so heat assisted magnetic recording is using heat to magnetically record data. Incredible explanation.
_wire_•2mo ago
dylan604•2mo ago
wmf•2mo ago
puzzlingcaptcha•2mo ago
retrac•2mo ago
So, to write, zap the area with a laser to heat it up. The coercivity is lowered. This lets a weaker magnetic field work to magnetize the area. This allows packing more densely, as the weak field will not affect the neighbouring cooler and higher coercivity regions.
(I think.)
This is not the first time lasers have been used to write to magnetic media. Magneto-optical discs (e.g. Sony's MiniDisc) were erased using laser heat. (MO discs also were read with laser, the ferromagnetic material used had different optical properties depending on magnetization.)