Hynix 48-GB Flash MCP

Hal_Porter writes to let us know that the third-largest NAND chip maker, Hynix, has announced they have stacked 24 flash chips in a 1.4mm thick multi-chip package. It's not entirely clear from the article whether the resulting 48-GB device is a proof of concept or a product. The article extrapolates to 384 GB of storage in a single package, sometime. Hal_Porter adds: "It's not clear if it's possible to write to them in parallel — if so the device should be pretty damn fast. The usual objection to NAND flash as a hard drive replacement is lifetime. NAND sectors can only be written 100,000 times or so before they wear out, but wear leveling can be done to spread writes evenly over at least each chip. I worked out that the lifetime should be much longer than a typical magnetic hard disk. There's no information on costs yet frankly and it sounds like an expensive proof of concept, but it shows you the sort of device that will take over from small hard disks in the next few years."

48 GB = 384Gb

[sirket]

The article does not extrapolate to 384 GB of storage- they extrapolate to 384 Gb of storage which is 48 GB of storage. bits != bytes.

Re:48 GB = 384Gb

[sirket]

JHust to clarify- the company mentions possibly going to 28 stacked chips which would be 448 gigabits (not gigabytes) of storage- or about 56 GB of space. Now as flash chips grow in size- this could double (assuming 32 Gb NAND chips which are becoming available) to 96 or 112 GB of storage or more (assuming larger chips).

Re:Why only 100,000 times

[jandrese]

It's due to the way Flash works. A flash bit is basically a conductor surrounded by an insulator. To store a bit, you apply a large charge to the insulator to increase the charge of the conductor, basically your burning through the insulator to get your charge though. Once it is on there, to read the charge you have to apply another large charge to the insulator and see if the resultant charge is n or n + m. The m factor comes from latent charge on the conductor.

Anyway, the upshot of this is that because you have to constantly burn charge through the insulator to use the part, eventually you basically burn out the insulator and cause it to leak charge. Once it starts leaking, you lose your stored bits and the part is useless.

Re:NAND flash writes

[TinyManCan]

This is straight bollocks. Its ridiculous to think that you could only write to a NAND block 1000 times.

Commercial products in the high-end flash space are promising 500,000+ writes.

We are not talking about glorified thumb-drive flash memory here, but decent chips with good wear leveling and high quality construction.

Re:HyperDrive4

[Surt]

Ouch that's expensive. And big (in physical dimensions) compared to:
http://www.computers4sure.com/product.asp?producti d=5623741&affid=10000483 [computers4sure.com]

I guess it may be somewhat faster, but both are approaching the limits of what you can push through a sata interface.

Not parallel

[RecessionCone]

It's not clear if it's possible to write to them in parallel -- if so the device should be pretty damn fast.

It's pretty obvious that it's not possible to write to this array of chips in parallel, because you just can't fit enough pins in a tiny package to provide the necessary interface for talking to 24 chips simultaneously. Also, take a look at the picture from TFA: http://www.koreatimes.co.kr/upload/news/070905_p10 _hynix.jpg [koreatimes.co.kr] - you can see that all the leads to the different chips are wired to the same pads. This doesn't prove my point - they could all be power or ground connections, but looking at the complexity of the packaging here supports the idea that providing a separate interface to each of these chips would be very expensive and difficult. In short, this is a capacity optimized device, it's not meant to break speed records.

Re:Why only 100,000 times

[networkBoy]

Flash is rated in erase cycles, not write cycles. Erase is the most damaging event to the tunnel oxide layer in the device, which is why they fail.
Flash Cell stackup (same for NOR and NAND, the interconnection of cells determines what type of array it is):

G - gate (metal)
ONO - Oxide/Nitride/Oxide layer
FG - Floating Gate (Poly)
tOx - Tunnel Oxide (very thin)
Si - wafer (NPN/PNP wells)

-nB

Re:Flash lifespan in persective

[smallfries]

You're assuming that the 2GB a day could be spread evenly over the disk. This would vary depending on how much free space you have on the device. If your drive is 1% full then you can distribute your writes over the other 99%. But most people don't keep their storage mainly empty. In fact people tend to run just under the limit - hence the saying that crap always expands to fill the available space. If your drive was 99% full then you can't distribute the writes over the parts with data (as it would have to be moved somewhere else negating the benefit), and then you run into the problem with the limited duty cycle.

Having said all of that, I don't think my throughput is anything like 2Gb, and most of it would be swap (hasn't happened much this past couple of years) and /tmp. Given that /tmp would be better suited to a RAM disk anyway I don't think that either would pose a problem, and the lifespan of these flash disks is probably comparable to a magnetic platter. As another reply pointed out, when the duty cycle is exceeded you can't alter the sector anymore. On a magnetic disk when a sector dies you're SOFL. Once the price comes down to an afforable level these drives will be beautiful...

Re:What about RAID?

[takev]

It is called P2

http://en.wikipedia.org/wiki/P2_(storage_media) [wikipedia.org]

From the wiki: The P2 Card is essentially a RAID of SD memory cards