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Why Not Solid State Hard Drives?
waterlogged asks: "I was just wondering if anybody has heard of a cheap ram based network drive? Seems to me with the ram prices being at about US. $12.00 for 128 megs that someone hasn't developed a battery backup version of this to plug into a network or even a bus. A gig worth of 8ns seek time storage for $120 anyone? That would just about eliminate any wait in loading programs."
BigSlowTarget asks: "There are some previous articles on Slashdot about vendors selling solid state drives, but they all seem to be quite expensive - particularly given the slide in the cost of memory. Has anyone hacked together a solid state drive to take advantage of $60/GB memory prices? I'd really like to be able to boot and run at solid state speed without spending thousands."
Jah-Wren Ryel asks: "In case you haven't noticed, RAM is incredibly cheap, you can put a gigabyte of PC133 RAM into your machine for less than $60. A year ago, that would have cost more like $600. So now it is feasible for one to have a 10-15GB RAM disk, except for one thing - most motherboards won't support more than 2GB total (4 dimm slots x 512MB per dimm). It seems like it wouldn't be too hard to design a PCI card to hold 20-30 dimms and make that available through a hardware windowing scheme (like EMS/EMM back in the old 16-bit days). With the right drivers it could be used as a big RAM disk or for buffercache. Is there such a product out there? The closest I have seen are solid-state disks that sit on the other end of a scsi bus, are too expensive, and aren't anywhere near as fast as a PCI implementation could be."
So what technical details (and the issues of volatile data and price) may be preventing the construction of RAM based drives, and is there anything else that may be preventing some entrepreneurial soul from bringing such a thing to market?
If only there were some sort of device which could store electrical power for later use.
RAM drives are a great idea, the problem is the IDE or SCSI bus. Seek times and retriveal times can be greatly reduced, but the total bandwidth is still a limitation.
Seagate had developed years ago a standard called IPI, I think. It was for the 30 and 40 megabyte RAM drives that had developed. I know it never took off, but it was specificlly for static RAM drives.
What would be really cool, would be RAM storage with an Infiniband interface. Its possible to use it for storage or for regular memory.
RAM is now cheaper when it comes to memory-per-unitofcurrency than hard drives.
According to pricewatch, a 40 gig hard drive is $78. Let's say $120 for a good one. That makes RAM 20 times more expensive, at $60/gig.
It's still really cheap, but let's not get crazy. :)
Sometimes it's best to just let stupid people be stupid.
The problem of how to maintain power to all that RAM indefinately is still pretty tricky, but how about this idea. Why not put enough SDRAM on your hard drive to buffer the whole thing? Whenever you read anything off the platters, hold it in RAM, and whenever anything is written, page it back to disk as usual. Thus as you use your system, the speed will continue to improve (up to a point) without tying up system RAM.
You are right. Cliff is wrong.
Given his figure of 128MB for $12, that's 10.66MB per dollar.
From western-digital.com I can get a 40GB 7200RPM UATA/100 caviar harddrive for $117.00. That's 341.88MB per dollar.
This puts harddrives into the lead by a factor of 32. So, until it's at the point where 128MB of RAM costs $0.375, harddrives still have the lead.
Justin Dubs
Given the plummeting price of high density/small footprint hard drives, you could have both the volatile drive and the nonvolatile drive in a single low price unit, with backup to/recovery from the nonvolatile drive occuring automatically on startup and shutdown.
It needs to be more often than startup/shutdown! Many of us don't shutdown for weeks at a time. You would want it to continually copy things to the disk when there is idle time. But then you're essentially using the RAM as a really big disk cache which is where we are already today.
As I read the article, the whole point is to shift to RAM and save money at the same time. If you're buying the hard disk anyhow then you're shifting to RAM but not saving any money. And you may not be improving performance much over a massive RAM cache either. So I find it hard to be enthusiastic about this idea of backing up the RAM to hard disk.
As such, they are fairly old technology, and most of the problems have been ironed out. The problem with power can be solved in a number of ways, for example. You can have battery-backed RAM, or you can have the "RAM" non-volatile by using a design that does not decay rapidly with time. (Flash RAM works this way.)
Another problem has been the capacity of a solid-state hard-drive. This, as has been mentioned, has largely been overcome. I =STILL= believe that wafer-scale chips are the way to go, for this, though. You should be able to make wafers that are tens of terrabytes in capacity, by now.
(The problem with making wafers has always been the purity and the defect levels. Purity just requires you to use something better than skimming. Double distillation, or atomic mass seperation, would give you near 100% purity. You then just cool the resultant in a vaccuum flask, so that the defect rate is negligable.)
Getting back to the modern day, though - how to turn cheap RAM into quality solidisk. This involves making a card, with a whole load of RAM on it. Since you're using conventional RAM, you can't rely on modern-day core memory. This means the fall-back of using battery-backed RAM.
You want TWO batteries, for this. One will be in discharge/recharge mode, the other will be in operational mode. When the batteries switch over, you want the recharged one to be switched first, so that the batteries are in parallel, BEFORE switching over the other. That way, there's no loss of power.
When switching to discharge/recharge mode, the battery must be fully drained, to prevent "memory", where a rechargable battery fails to recharge correctly from a semi-charged state. Once drained, you recharge it to capacity.
The switch-over should happen on one of two events:
This guarantees that you have 175% - 200% of any one battery's lifetime, which should be ample for most purposes. The recharger should tap off the bus' power supply, with the batteries directly powering the RAM at all times. This avoids any problems of messy spikes somehow getting into the computer.
If you want "extra-long-life" SSD technology, you are probably best off using very low-power RAM for the main disk, and using higher-power fast RAM for the cache. The lower the power of the main disk, the better. Static RAM is worth a glance, for this - I think it's usually more efficient than dynamic.
Of course, the =ULTIMATE= solution is to go back to using core memory. (For those who never went to computer science classes, "core memory" is one of the earliest non-volatile digital storage systems. It was a form of magnetic storage, and used semi-permanent magnets to retain the data. Data could only be read by destroying the copy in storage, which mean that a read cycle also had a write cycle. It was slow, but when you had RAM that was guaranteed to retain data for over a century, who cared?)
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
You point is correct but the parent's point is correct as well. We may have 40GB drives, but we are only using a small amount at any given time. Using the strengths of RAM with the strengths of HD's we could see some really interesting hardware. It seems like the middle road (similar to what another poster mentioned) is to substancially boost the amount of RAM used as a disk cache. Add some pseudo-AI drivers and you end up with a situation like this.
User starts Word. As the application is loading and initializing and as the user is working, the hard drive is automatically loading all dictionaries, the other Office programs, the equation editor, the charting program, the clip art, the help files, all .docs you've ever edited, all .txt files, local .html files into your 2 GB RAM buffer on the hard drive. You may never, ever use Word to edit html files, but since RAM is so cheap it doesn't matter.
A complete directory of all files is also stored in the drive's RAM buffer. Searches become instananeous.
As you save files, the saved files are mirrored back to the platter to ensure against power failures, but they are also saved in RAM (with a battery backup) to ensure against head crashes.
Now that the hard drive has memory to burn (so to speak) it stops being a mere storage device and becomes a "autonomous storage unit" that has it's own CPU to assist the computer in it's search for information. Seagate, Maxtor, and all the other drive manufacturers who are about to declare banckrupcy start marketing "ASU : Storage for the 22nd Century" in partnership with the struggling memory companies (who would love to have another market for the slower / cheaper memory technologies).
The technology companies are saved thanks to my idea (until, of course, we find out that Rambus actually owns the patent on ASU's and they start sueing everyone ;-)
Waltz, nymph, for quick jigs vex Bud.
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:)), one machine could replace them 10 with only that little step up. Thing is I can't afford 10 machines and the drive subsystem, nor current SSD solutions.
To take advantage of RAMdisks, you pretty much need to have your computer on all the time, or in standby mode when you're not using it. At this point, what do you need much higher disk bandwidth for?
Loading your mp3s or movies?
Loading office in 2s instead of 6s?
running your games (oh wait, that's CPU/GPU intensive not HD).
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FORGET ABOUT HOME USE, think a bit.
There are limiting factors with hard drives, mainly LATENCY issues, this might not be a problem for you or any home users, but for some specific scenarios, it is, and a BIG one. I give you a specific case where I could benefit from such a system:
Without going in too much details, I work with a lot of files, my workstation generates over 200,000+ files for a single simulation, no it can't be put in a database for now, it has to be accessed from different software with no database support, every other part of the software is optimised to know exactly which file to open, using the maximum of memory, cropping useless data, etc etc... everything is maximized to a more than good level. The only bottleneck I have in my system right now is the drive's latency issue, and beleive me, if I could go down from the milliseconds to nanoseconds or microseconds, it would be over a tenfold increase in speed and I wouldn't need 10 machines running in parralel to do the job in one day (which unfortunately I don't have
Most application are bandwidth hungry, but there are some stuff out there requiring LOW LATENCY, and heck, if there wasn't a need for that, you wouldn't see solid state drives for 60,000$ out there. There's a need, but sometimes you're limited by your R&D budget and you'd gladly take an emmerging technology or home-made stuff if it means saving 80% of the cost of the equivalent part, and increasing your effeciency by a factor 10.
I'll see your answer "if you need it, and it slows down you r&d, buy it, for the sake of the company" sometimes it doesn't work like that for cashflow reasons and you have to work with what you can get in your specific budget, the issue here (and title of this forum) is about cheap storage that would have a low latency and High bandwidth solution (with loads of storage). I'm sure I am not the only one that would GLADLY grab a 30GB solid state drive for a fraction of what it would cost me with the current systems (which are way overpriced considering the price of ram right now).
There's a need for Solid State, while I understand that the gap between a home user and a workstation/server class machine is blending more and more, it's not because a home user wouldn't benefit from such a device, that it's not needed for corporate or R&d levels. Current solutions wouldn't be selling for 50K$+ if there wasn't a need for them... heck, they wouldn't exist.
--- Metamoderating abusive downgraders since my 300th post.