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back to article They said it wasn't right for biz - but Samsung unveils TLC SSD

Samsung's South Korean headquarters has announced two new 840 SSDs, one of which uses three-level cell (TLC) technology , a first for the industry, and the other a more normal two bits per cell, the 840 Pro. The 840 Pro is, according to one of several reports a SATA 6Gbit/s interface product, delivering 100,000 random read IOPS …

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Anonymous Coward

I've gone for large capacity.

My reasoning is that if I have 100Gig which never changes, and 20 Gig which changes a lot, then I get 10,000 * (120 - 100) / 20 changes on a 120Gig drive. == 10,000 rewrites.

But on a 500 Gig drive, I get 10,000 * (500 - 100) / 20 == 200,000 rewrites.

Or am I wrong?

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Bronze badge

Re: I've gone for large capacity.

It depends.

The number of rewrites is only given "per cell, on average", which is very different to the real-world maximum. You might find that it writes the same cell over and over (even with wear-levelling) and burns through the replacement "spare" cells too, writing that same information, and you end up with a worn "hole" in the disk even though millions of other cells are untouched.

The wear-levelling algorithms are not perfect, and the averages given mean that any write could fail and bring in spare cells to replace a broken one, regular or not. It really depends on how much "spare" capacity you have to be able to bring online should a cell fail more than anything else. With 500Gb, you're likely to have less spare (proportionally) than a 100Gb.

I'd actually care more about just using the drive normally and choosing a manufacturer/model with a good reputation than any advertised statistic, though. Base it on real-life experiences, buy the "older" model with more good reviews and less "it just died on me", which would tend to be the smaller one, and would also tend to cost more than equivalents of its size (even to the point where you could get a 256Gb for the price of a particularly reliable 128Gb).

Or, don't use it for permanent storage and just realise you're going to kill it like any other drive. Have a spinning disk for actual data, and an SSD for "working storage" (e.g. games, Windows, things that can be replaced and don't actually matter).

People keep telling me that spinning disks have a lifetime and die. The only disk I've personally witnessed dying without giving LOTS of warning before hand (e.g. SMART etc.) was actually 20Mb. Ever since then, I've seen disks that report 1-2 bad sectors and you can just rewrite those sectors and get around it (either the disk pulls in spare sectors, or the OS marks them as bad and doesn't try to use them), or they just keep going. Hell, I have a stack of disks at home that go back to 386's.

Buy it, expect it to die, don't rely on maths based on adverts to base your averages on, back up anything critical on a couple of disks of differing technology to cover your ass.

SSD's are really just consumer items now. You're probably NOT going to hit the write limits at all in the lifetime of the drive but, like with any consumer item, it's possible it could blow up on the first day.

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Re: I've gone for large capacity.

Not all SSD are created equal - SLC SSDs can sustain writes on orders of petabytes and that's why they are used in the enterprise sector.

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Anonymous Coward

How I learned to stop worrying and love TLC

A sudden inspiration about why TLC might not be *that* bad - as SSD capacity increases to the point that an end-user can keep all their stuff on the drive, all the clart that never changes (mostly pirated content, aarrr) will take up an increasing proportion of the drive. The number of blocks that get rewritten is probably dependent on the OS and use pattern - so on the "big drive filled with junk" those writes can be spread over many more flash cells and drive lifetime should be no worse than a smaller drive that uses two-level flash.

I think we'll see more mainstream laptops coming out with this sort of TLC drive now that capacity points are comparable to HDDs. Hower there remains a lurking fear that there will, from time to time, be spectacular data loss incidents.

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Re: How I learned to stop worrying and love TLC

"from time to time, be spectacular data loss incidents."

And this differs from HDD how ?

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Joke

Re: How I learned to stop worrying and love TLC

"And this differs from HDD how ?"

Less 'clicking' noises.

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Windows

Re: How I learned to stop worrying and love TLC

"And this differs from HDD how ?"

When a HDD fails at least you can open it up and extract the strong magnets it contains. Dead SSDs aren't nearly as much fun.

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Re: How I learned to stop worrying and love TLC

I once spent an instructive afternoon smashing drives with my dad. We had a load of them that needed to be destroyed beyond recovery, so we took at them with a chisel, sledgehammer and a bench-grinder.

Things were going well, and we had a stack of magnets so high they were starting to topple even with the neodymium strength, until my dad struck the exposed platter on one with the hammer. Turns out it was some kind of glass, that shattered into millions of pieces. It was the only one not to have a metal disc.

Data destruction achieved, but the sweep-up took longer than we thought.

When SSD's come along, guaranteeing data destruction isn't going to be as easy.

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Anonymous Coward

Re: How I learned to stop worrying and love TLC

Original AC here...

> "from time to time, be spectacular data loss incidents."

> And this differs from HDD how ?

it's very rare for a failing HDD to suffer massive data loss. Usually the bad areas render the system unreliable/unbootable while it is still possible to get most of the data onto a new drive using dd_rescue or similar. On the other hand of the SSD failures I've had to deal with, two were 100% data loss and the other was about 50%.

The only recent HDD recovery failure was an external HDD that was dropped while powered up. That's one use care where SSD would have been a lot better.

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Re: How I learned to stop worrying and love TLC

"When SSD's come along, guaranteeing data destruction isn't going to be as easy.

"

BLOWLAMP !

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Re: How I learned to stop worrying and love TLC

Or industrial shredder.

http://www.youtube.com/watch?v=Wp8sFsriH4c

Go on, you know you want to.

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Anonymous Coward

SSD secure erase

Actually its pretty easy to ensure data destruction on an SSD.. Because it's just memory bits you can just flip all the bits to 1's or 0's. Job done. As long as the vendor has correctly implemented the secure erase function all good. Magnetic dipoles are much harder to erase because each atom can be a dipole.

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Anonymous Coward

Re: SSD secure erase

I also once spent an afternoon trashing my drives. But I bent them with mole grips, having first lifted them out of the case (I enjoy taking things to bits.)

It was all going well, until I got to some modern drives, when on grasping them, it turned out they were made of glass or something. Cue tiny bits of glass embedded in skin.

SSDs are easy. A pair of CK side cutters through each flash ram chip. 20 seconds.

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Bronze badge

Re: SSD secure erase

Fabulous. So you find a 10-year-old SSD in the back of a server room. You don't know what's on it, but it could well be financial details. It doesn't boot up, the drive controller doesn't recognise it at all, and there's no buttons/resets on the drive whatsoever. A data recovery firm will charge you several thousand pounds just to get the drive back to operational to find out what's on it or issue a secure erase command (if that's even possible by then).

ATA secure erase commands predate SSD's by about a decade. There's a reason you don't rely on them. When a drive dies, you still need to destroy the data, but you can't make it do it itself. You tend not to replace drives unless they've died or you don't want to waste time cleaning them up for re-use. And waiting hours while each drive of 1000's is powered on, issued an erase command and waiting for its successful completion (which could still take hours) is the least efficient way possible to destroy the data (the most efficient being to throw things in a fire until there's no recognisable components left).

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Silver badge

Smashing time with glass disks

There is usually a small whole in the outer casing with a foil sticker covering it and warning label. I peel the label off, pop a punch through the hole and hit it with a hammer. Not quite as satisfying as using a sledge, but a lot less mess to clean up and they do make a really satisfying noise as they go :-)

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Anonymous Coward

PASS

The SSD makers can't make traditional MLC NAND reliable in consumer grand SSDs so why would anyone but a fool touch TLC SSDs? Fools rush in where wise men dare not tread.

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Happy

The Glass ones are better!

Speaking with my tin foil hat on, I do enjoy a bit of drive smashing. The glass ones are a hell of a lot easier to trash than the metal platter ones.

My metal ones i had to destroy in a hurry, so a bit of rum and coke, scratching with a magnet (and also a screwdriver) and leaving them outside in the middle of a Canadian winter was the best i could do at the short notice. I know that probably not enough to destroy the data but hopefully it was enough to prevent someone trying to access the data (aka too much effort to bother).

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Boffin

Actually the shredder isn't a sure thing

Read a very interesting paper about shredding flash chips, most shredders don't actually make small enough pieces to be sure of destroying the flash die on a PCB.

If you really want to destroy the data on an SSD several hours in an oven will do the trick, (make sure its not too high, don't want to set it on fire) after a while they will be good and scrambled.

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Anonymous Coward

Nobody will be lined up to buy these

I suspect Samsung will need to fire sale price these to get any technically knowledgeable company or consumer to buy these.

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