Why SSDs Won't Replace Hard Drives 315
storagedude writes "Flash drive capacities have been expanding dramatically in recent years, but this article says that's about to change, in part because of the limits of current lithography technology. Meanwhile, disk drive densities will continue to grow, which the author says will mean many years before solid state drives replace hard drives — if they ever do. From the article: 'The bottom line is that there are limits to how small things can get with current technology. Flash densities are going to have data density growth problems, just as other storage technologies have had over the last 30 years. This should surprise no one. And the lithography problem for flash doesn't end there. Jeff Layton, Enterprise Technologist for HPC at Dell, notes that as lithography gets smaller, NAND has more and more troubles — the voltages don't decrease, so the probability of causing an accidental data corruption of a neighboring NAND goes up. "So at some point, you just can't reduce the size and hope to not have data corruption," notes Layton.'"
There are always more axes of improvement... (Score:4, Interesting)
With SSDs, I'm sure there is always another axis of improvement, similar to with CPUs, when you hit a wall with them, go SMP. When SMP doesn't scale, crank up the clock speed, etc.
What I wonder is what can be focused on to make SSDs be able to store more. We can always stick more chips in an enclosure, and the cooling needs for SSDs are far less than the cooling needed for CPUs.
Re:Selective evolution (Score:5, Interesting)
It is kind of funny how the article seems to be non-inflammatory, saying that replacement won't happen "soon", but the headline reads like a nice troll. Anyone think the editor chose the headline for page hits?
Re:There are always more axes of improvement... (Score:2, Interesting)
Yeah, my first thought with SSD was additional parallelism and such. It seems pretty obvious not only to improve capacity but to improve speed as well. Seems like a no-brainer to me.
Who knows what the real intention of this article may be, but as far as I am concerned, "SSD" isn't ready enough yet. It's nice, but the ones that perform well are ridiculously pricey and the ones that are somewhat affordable are ridiculously slow. It's simply a deterrent for me at the moment.
Re:There are always more axes of improvement... (Score:3, Interesting)
Exactly. Since the form factor isn't dependent on a disk shape, it might be better to go with a form factor that is better for SSD. Perhaps cubic, with a riser card holding the banks of flash chips connected to the controller which does the ECC, encryption, wear levelling, and other stuff?
Re:There are always more axes of improvement... (Score:4, Interesting)
Re:There are always more axes of improvement... (Score:2, Interesting)
We might end up with two types of SSD, or even drives with both:
MLC's descendant would be designed for space and shoveling as much data into a drive as possible. Because of this, it would require large amounts of error correction. Because MLC is sometimes less reliable than SLC, it will take more processing power to encode incoming data effectively and safely.
SLC's descendant would be designed for speed.
As time goes on, operating systems will get intelligent enough to figure out what parts of a volume are most often used, and move them to the SLC array so they are accessed with a faster speed, while items that are not accessed go to the slower MLC array.
Is physical size really the problem? (Score:2, Interesting)
Re:Do we always need more space ? (Score:2, Interesting)
Re:Not just density (Score:3, Interesting)
There has been breakthroughs in voltage (Score:3, Interesting)
Re:Limitations aren't the tech of the NAND chips.. (Score:5, Interesting)
Correct me if I'm wrong here - and I usually am wrong -
I'm usually right... but that statement might be one of the exceptions. :)
TFA doesn't actually make any arguments about price directly. It indirectly suggests price of the drives is related to lithography resolution, but provides nothing to back that up.
It seems to me that over time as yields on current technology increase and fab costs are recouped, the price of current technology will go down.
It's a basic maxim of the silicon industry that cost is directly proportional to die area. To simplify, you can consider the silicon fab to have a fixed cost per wafer. Therefore the more die fit on a wafer, the cheaper each chip becomes. The two main ways to do this are by reducing the amount of functionality on each chip (undesirable when the goal is to increase capacity), or to move to a smaller lithography so you can fit many more die on a wafer. While new lithography generations have frequently allowed greater performance, even if they don't they are deployed anyway because it reduces cost for the manufacturer.
Yield improvements and paying off R&D both will help cost, but only to a limited extent. Yields for a production lithography should already be quite high and will asymptotically approach 1. Once R&D is payed off the cost will drop, but there still remains a very large fixed cost per wafer. Neither is going to come close to the cost benefit of being able to, say, go from a 45nm to 32nm process and get roughly 40% more die per wafer.
So yeah price will come down for other reasons, but in the long term price reductions in flash memory devices are going to depend on using smaller lithographies just like it does for other semiconductor devices. The author probably just didn't think to explain this aspect of it, since it's such a well-known aspect of the silicon industry.
On the other hand, people were saying that CMOS processes used in CPUs were going to reach fundamental limits 20 years ago. And 15. And 10. And 5. And oh sure, some of those limits were reached, but then clever people worked around them. The statement in the article amounts to "We can't just blindly reduce lithography size without changing anything else indefinitely", which is true but also kinda pointless since the people working on smaller lithographies for flash are probably aware. In the end exponential progressions like this can't last for ever, but I'm not about to tell the process engineers that they aren't going to be able to find enough tricks to keep it going long enough.
Re:Just bought WD 64GB SSD (Score:1, Interesting)
yes. I purchased a Corsair Force 120GB for a new laptop yesterday.
My current laptop is 250GB, but I don't need all of that storage. The increased battery life and vastly improved reliability, not to mention the huge speed make SSD highly desirable.
No brainer. Spinning media for the average Joe is stupid. In 5 year only those with large video collections will want a rotating platter.
Re:Expanding drives (Score:4, Interesting)
The most interesting man I never met lived in a small house near the beach, had newspapers and old chairs and magazines piled to the ceiling in every room. Must have had a thousand cubic feet of Life Magazine. A most exciting fellow. What the man could have done with a proper warehouse, who knows?
What will finally put Seagate out of business is the universal porn compressor: an algorithm to produce almost any image with a pornographic payload (validated through fMRI studies). Finally we can eliminate women from sex. It'll be great.
Re:They suck anyway (Score:2, Interesting)
I agree. I thought this was going to be an article about something new instead of just throwing in the word lithography into a tired old argument.
I bought an SSD after by HDD overheated and died in my netbook. I bought it on ebay because I was trying to be stingy. Turns out it wasn't a good choice. It runs pretty darn hot and doesn't reduce power consumption that much. It is not appreciably faster. The worst part is it isn't universally well known which is important with linux. I often get Grub Boot error or other system freezes for no apparent reason. Also it can be really slow for some write heavy applications. Overall I wouldn't do it again. The only good aspect is that at only 32GB by collection of downloaded nonsense can't get too big or out of control so I don't have to worry about backups as much because it isn't so big... and I get more work done with less movies on there to watch.
What I really want is a cooling mechanism for a normal HDD that sits inside the case (not a bulky laptop pad). I really don't think it is acceptable that the disk burns up under normal usage on a hot day. Things are just packed too tight and I have yet to find any after market add-on I can use to keep the temperature reasonable. I always have fans in my desktop because I know temperature is inversely proportional with HDD lifespan and I don't enjoy disk failures.
SSD was a real dissappointment for me. I was willing to trade storage capacity for the supposed benefits of cooler, less power, quicker, less likely to fail. But the disk I bought doesn't seem to deliver on any of those fronts in any signifigant way and the reliability is indeed less: with a spinning disk I know the typical problems and solutions and ways to make the most of it. With the SSD I have no idea why the system periodically freezes, or if it is trustworthy given the whole weirdness about having SSD specific filesystem requirements that I can't decide which method would be a wise so I stick with EXT4 and hope things work out.
Re:So let's get some hybrids then! (Score:1, Interesting)
You mean something like this?
http://www.tomshardware.com/reviews/seagate-momentus-xt-hybrid-hard-drive-ssd,2638.html
The review was pretty much a failure because they tested on a brand new drive with a fresh OS install before the caching algorithms had a chance to work, but the drives exist.
Lots of people use 2.5" drives in desktops these days. I'm guessing you want the one that comes with a heatsink and 10k rpms.
Re:Solid state densities (Score:2, Interesting)