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Why Not Solid State Hard Drives?
from the why-use-platters-when-RAM-is-cheap dept.
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?
Needs constant power (Score:3, Insightful)
Re:Needs constant power (Score:5, Funny)
Re:Ummm CMOS? (Score:4, Informative)
Re:Not a problem (Score:5, Insightful)
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.
A long time coming (Score:3, Funny)
Re:A long time coming (Score:5, Interesting)
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 ;-)
Solid state drives. (Score:4, Informative)
Cenatek [cenatek.com] 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.
Re:Solid state drives. (Score:4, Interesting)
According to their website, sustained data transfer rate is 80-100MB/s (umm, WHY would it vary if it's all solid state?). Add to the fact that the PCI bus is limited at 133MB/s and there's more than just 1 device using the PCI bus (and a lot of them aren't conservative when it comes to bus usage)...
Or, for 1/4 the price you can pack together 2x75GB drives in a raid 0 array, get 30x as much space AND get the same bandwidth.
No, right now there's not much point to solid state drives. Iff (sorry, math hangover, If and Only If) hard drive prices were to stay the same, and memory prices were to fall by an order of magnitude (lets say 10x) THEN I could see there being a market for this. But you'd also need to use either PCI-64 (533MB/s+) or get some other designed bus to support the much higher throughputs.
But then again this just begs the question, what do you need that much more speed for?
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).
Quite frankly I don't see the technology or the market right now to create solid state HDs.
finally -- a use for AGP! (Score:4, Interesting)
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.
Re:Solid state drives. (Score:5, Interesting)
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).
--
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.
Re:Solid state drives. (Score:4, Insightful)
I'm sorry but you really need to go back to drive technology 101
Idiots like you shouldn't talk out there ass so much...
You must be one of those who
I'd call you stupid names back in return, but I don't stoop that low. Anybody who needs to do that (a) needs a lot more fiber in their diet and (b) needs to lighten up.
I HAVE a 4x75GB IDE RAID 0 array, and can get a max of 98MB/sec read off of it, and a good 75MB/sec sustained. Off of a single drive I can get 45MB/sec max, 25MB/sec sustained.
And I was implying that there are very few applications that need the use of that specific RAM disk over a much cheaper IDE raid array. If you had 4GB RAM on the mainboard, or 8GB or 16, then you would see a few more apps that would benefit from that performance. However just about any home user, and the vast majority of corporate users wouldn't benefit one bit from the use of that. There are very few uses that would benefit from a sustained 90MB/sec, however the very low latency is a big help.
So I wasn't "talking out of my ass". Go shove your nasty attitude up someone elses ass. Like we don't have enough problems to stress over as it is. Lighten up.
RAM Drives. (Score:5, Interesting)
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.
Re:RAM Drives. (Score:5, Interesting)
The main performance benefit of a RAID is in reducing the impact of seek time on overall throughput. You pay a little extra in transaction overhead to send commands to multiple drives (instead of a single drive) to gain the dual benefits of cutting the average cost of a seek down, and increasing your linear access bandwidth. (In other words, you do seeks 1/N as often, and your bandwidth for a linear read within a track is N times what it would be for 1 drive, for a RAID with N drives. At least, this is true for striping.)
With a RAM disk, the cost of seeking is zero. Also, the bandwidth of the RAM already exceeds the available bandwidth of the drive cable. So, if you were to RAID your RAM drives, you'd still have the performance penalty of the additional overhead, but no gain due to hiding seeks or striping your bandwidth. The result would be a net loss in performance.
Now, what might be interesting is a mirrored RAID, where one side of the mirror was a physical HD, and the other was RAM. Modify the RAID software to send all reads to the RAM drive by default. Ta-da! Instant hardware-backed RAM drive! Performance would be lower than a pure RAM drive, but you wouldn't need to do anything unusual to make the RAM's contents persistent. A power loss looks like a drive failure -- just replicate the other drive back to the RAM.
--JoeHuh? (Score:4, Insightful)
Huh? Unless I'm completely out to lunch, I don't see this....
Is my math wrong, or is Cliffs?
Re:Huh? (Score:5, Informative)
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
Re:Huh? [OT] (Score:4, Insightful)
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 [slashdot.org] was so pathetic it didn't even qualify as satire. It should never have seen the light of day on either
And
Cenatek (Score:4, Informative)
From their site:
The Rocket Drive stores data in memory modules (standard dynamic random access memory, or DRAM) rather than on magnetic media.
The illegal use potential (Score:4, Funny)
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...
Ram drives, nothing new (Score:3, Interesting)
Huh? (Score:5, Informative)
RAM is now cheaper when it comes to memory-per-unitofcurrency than hard drives.
According to pricewatch [pricewatch.com], 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. :)
Linux is good at that... (Score:3, Interesting)
How about integrated buffers? (Score:5, Interesting)
Size does matter... (Score:3, Insightful)
Recovery (Score:3, Interesting)
flash drives (Score:3, Interesting)
i have been very pleased with my sandisk [sandisk.com] flashdrives. basically they are IDE-interface drives with flash memory instead of spinning platters. 0 ms seek time is nice, so is -silent- and -very very low power- storage. not to mention if you don't have to treat it like an egg.
i've used both the flashdrive [sandisk.com] from sandisk, and the IDE flash drives [simpletech.com] from simpletech [simpletech.com].
the sandisk flashdrives have sizes from very small (4 MB) to big enough for your MP3s (2 GB). of course they get expensive at the high end :) best things about them are (1) can get them semi-cheap from ebay [ebay.com] and (2) standard IDE interface.
-samATTO SiliconDisk (Score:3, Informative)
You don't necessarily need a RAM disk (Score:3, Insightful)
There are two ways you can do this.
Way 1 -- Use a PCI card with 4GB of RAM on it as primary storage. At the end of the day, or week, or whatever, copy all of the data to more "permanent" storage. Like hard disks. This way a power loss (or battery failure) isn't too much of a nightmare.
The drawbacks are that you need special hardware and you could lose days of work.
Way 2 -- Cram your machine with as much RAM as possible. Which probably means 4GB. Configure your OS so that it uses about 95% of RAM as a buffer-cache.
Data will be loaded from disk initially on demand (which means slow startup) but will almost always stay memory resident thereafter. The OS will also commit dirty pages back to disk from time to time ensuring that you don't lose anything important.
This may be less doable with systems that insist on synchronous writes during file operations, but you can often disable these things if you want to take the risk.
The benefit of this approach is that you don't need special hardware and you're less likely to lose data than Way 1. Which basically means you can and have been experiencing this now.
If your system grinds disk consistently after several hours of use, it's a good indication that you should get more RAM considering how cheap it is.
SSD's aren't new (Score:3, Informative)
We actually got our Alpha vendor to let us try an SSD for 30 days. The drive was fast, but we found that we quickly saturated the controller (something a couple U160 drives can easily do). In that regard, it wasn't that fast at all.
And, as has been said in other posts, it's not really economically fesible. We tested a 3.2GB SSD last Christmas that cost $25,000. For that application, we thought it was a good fit. But if you're concerned about capacity, we just bought some 180GB drives for our SAN for about $5,000.00 each.
While the RAM and disk capacity available now is amazing, I don't think we'll ever see the dollar/cost ratio for RAM beat the dollar/cost ratio for disks.
In 1994, which I had a 486/DX2 66 (which came with 4MB Ram), I bought 16MB of RAM for $560.00. Quake was 15MB, so I could load it into a ram drive and play from there. Guess what? It wasn't noticably faster than my IDE hard drive, but Windows screamed. =)
Missing the point of SSDD (Score:3, Interesting)
In order to explain I'll have to do a quick primer on RDBMS' and how they handle memory management.
As you're probably aware, there are a multitude of different operations you can perform on a RDBMS; UPDATE, DELETE, SELECT, etc.
For more efficient queries the RDBMS will cache physical data structures in memory. It may cache parts of the index or recently accessed data. If the cache is full it will kick out the oldest, least used parts to make some room for the new stuff.
To make a long story short, most servers have way more disk space than RAM. As such, it will use a designated 'temp' or scratch area for some of those sorts (and temporary tables) if there are more important things in RAM or it cannot all fit. In Sybase / MS SQL you create a special database for this called 'tempDB'. I'm sure DB2 / Oracle have similar data structures.
Here is where solid-state disks enter the picture. You can buy a small solid-state disk (9GB or less) for cheap. You then 'create' tempDB on the solid state device. That way you can completely eliminate the relatively slow disk drive for things like sorting, temp tables, etc. and devote all of your RAM to caching database information.
To me, this seems a lot better than using solid-state devices exclusively as a storage medium. Initially when you start up your RDBMS the cache is clean. After people run a couple queries the important (and most hit) indexes and data are cached any way so you do not have to worry about touching the disk unless you perform a write. However in most OLTP (online transaction processing; a la web app) it's mostly selects so you wouldn't receive the benefit of the solid-state device unless it wasn't in the cache.
Most SSDD have a battery-backup in them in case of power failure and are generally mated to a corresponding hard drive. When the SSDD is idle it will flush the writes to the HD to keep the HD up-to-date. On a power failure it will immediately dump changed data to the HD (also battery-powered).
For 'home' systems I can't imagine anyone using SSDD as their primary storage. It doesn't make sense - rarely does anyone perform anything that 'demanding' as to require solid-state drives. Plus, if you have a single memory error you would lose the entire thing (break one of your DIMMs and tell me what happens when you try and boot.)
OS Redisign (Score:3, Interesting)
We would have to do some serius os and user interface redesign. If the pc is used for video editing the samples could be kept in memory this would speed thing up a bit, but you would have to save the data to the HD eventualy.
Another great application for this would be chase servers, imagin a organization that does video editing and all the clients have gigabit ethernet, implement servers that have 1TB of ram before the data storage server at night they could sync the data.
Seriusly, we have to think about this, our current view on pc is that ram is way more that hd storage. Diskless clients could make a come back...
Solidisks, and other Solid State Technology (Score:5, Interesting)
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?)