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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.
(heh. oops.)
Cenatek seems to be on a good track with these. They offer a PCI card with a handful of DIMM slots, a slap on rechargable battery panel, which holds enough power to run a connected hard drive of appropriate size which will dump the contents of what is essentially a RAM disk, in the event of a shutdown or power loss. A little spendy still, for consumer use, but to see something like this backend busy websites, or store database file structures would be pretty slick.
- billn
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.
Huh? Unless I'm completely out to lunch, I don't see this....
Is my math wrong, or is Cliffs?
Cenatek may make exactly what you're looking for. It's a PCI card, and uses standard SDRAM sticks.
From their site:
The Rocket Drive stores data in memory modules (standard dynamic random access memory, or DRAM) rather than on magnetic media.
L337 script kiddies would no longer have to worry about their Hard Drives telling the tale of all of their l337 ownz3r!ngs. As soon as the feds show up yank the plug.
This would also work for War3z fiends. *again, yanks plug* "What do you mean piracy, I don't even have an OS on there."
Seriously, I think it would only be useful if you could couple it with a RAID-like (I know it wouldn't be true RAID) system so if the power for whatever reason (Power outage, UPS goes bad, battery dies) you info wuold still be there, maybe a RAM-drive that does nightly/hourly back ups...
Note to self: No more arguing with the faithful.
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.
Your CMOS is something different, actually. Most computers use "DRAM", which needs to be "refreshed" often, or it'll "lose it's charge"... ROMish stuff is SRAM, which doesn't need the stupid refreshes... But it's more expensive, so a a couple gigs of SRAM is sorta out of the question. :(
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suwain_2
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.
The slashdot crew over the past few days/weeks have been extremely out to lunch, has anyone else noticed this?
/. or Salon.
/. gets over 200 story submissions per day, and yet the average number of story postings has gone way down, now to about 10/day. What's going on here?
Example 1:
but RAM is now cheaper when it comes to memory-per-unitofcurrency than hard drives -- cliff
RAM is 30-40x more expensive than HDs, I don't know WHAT he was smoking when he thought that...
Example 2:
I suspect a fair number of people never try Linux or one of the BSDs because they're moderately happy with AOL as an ISP -- timothy
how many people do you know who would be running Linux if it wasn't for the fact that they were using AOL? (Let me rephrase, how many tech savvy people are using AOL (that aren't forced to)?)
And the anti-Microsoft hysteria has been especially harsh over the past few days. That article about File Extensions And Molopolies was so pathetic it didn't even qualify as satire. It should never have seen the light of day on either
And
If God gave us curiosity
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.
This is exactly what AGP was designed for -- high-bandwidth I/O to main memory, without blocking the PCI bus. Plus, the AGP GART can do most of the address translation you would need. All modern PC (and even Apple) chipsets have an AGP interface, which is wasted on a headless server. . . until now. AGP even provdes extra power (even the obscene AGP PRO), so that an onboard battery/HDD could be used to backup.
> 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.
This is true. *or* you could have your computer net-boot from a a server with one of these. Even 100megabit transferring from memory will feel faster than a local hard disk. And gigabit over copper is becoming very affordabl these days.