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Ask Slashdot: Breaking the Computing Bottleneck?
MidKnight asks: :
"With CPU speeds venturing into the GHz, typical DRAM
access times falling towards 6ns, and network speeds trying
out the 100Mb waters, the major computing bottleneck
continues to be the hard drive. While other hardware
speeds grow in orders of magnitude, hard drives aren't
much faster than they were in the 70's. So, the question
is, when will mass storage speeds start catching up, and
what will the cause the revolution?"
You can think of all the storage space in your computer as being arranged in a heirarchy from fastest to slowest: CPU registers, L1 cache, L2 cache, RAM, disk, nonlocal media (network, tapes sitting on the shelf, etc.).
The CPU works directly on registers. When it needs something else, it sends a request to the next level, L1 cache. If it's not there, that level requests the data from the next level, and so on. The first four levels of the memory heirarchy are fairly close to each other in performance:
- Registers are zero-latency by definition.
- L1 cache is very nearly zero-latency.
- L2 cache requires the CPU to idle for a couple of clocks while waiting for the data.
- RAM makes the CPU wait for a few dozen cycles in the best case, on a fast bus.
And then there's the disk. Disk latencies are measured in milliseconds. With a modern 500-MHz CPU, a millisecond means 500,000 cycles. When the CPU needs data from a page of virtual memory that's on disk, it has to wait millions of cycles for that data to be loaded into RAM so it can then fetch the data.That's five orders of magnitude worse than RAM (by contrast, RAM is one order of magnitude worse than L2 cache). This is why virtual memory thrashing is so disastrous for performance.
RAM-to-disk is the biggest critical gap in the memory heirarchy. SCSI hardly does anything to close the gap. A 7-ms latency is not much better than a 9-ms latency-- it's still millions of cycles-- and SCSI's higher transfer rate doesn't mean a thing for virtual memory since pages are pretty small to begin with.
OTOH, applications that are limited by transfer rate rather than latency may benefit from SCSI, but transfer rate has never been the big problem with hard drives.
~k.lee
Researchers at the Hitachi Cambridge(UK) Lab at Cambridge University are developing a new memory device named 'PLEDM' - Phase-state Low Electron (hole)-number Drive Memory, which they believe to be 'a promising candidate for the multi-Gbit memory chip which is scheduled to become available early in the next century'. In principle, it is possible to make a fast non-volatile PLEDM cell by modifying the barrier-structure in the channel, and they are confident that many of the present day data storage devices (eg: computer hard disk drives) could be replaced by PLEDM in the future.
The Hitachi press release
Is faster yes, the problem is that as long as we use a spinning platter to store data with a physical head moving around it that imposes some limitations. The platter spins at a finite speed and the head moves again at a finite speed. We need some sort of solid state mass storage, the problem is that is *MUCH* more expensive.
--Zach
Erlang Developer and podcaster
Actually, diamonds would be an excellent choice, were it not for the DeBeers family. You see, the hell of it is, diamonds aren't even all that rare. It's just that the DeBeers family owns all of the known mines. They exercise monopoly power in ways which would make Bill Gates look like RMS, and that's why diamonds are so expensive.
Diamonds aren't that tough to manufacture in labs, either, believe it or not (after all, diamonds are just carbon, which is plentiful; add a bit of boron and you get one hell of a semiconductor).
However, you still have one major problem: speed. Consider the following: CD/DVD has made creat strides in the past years speed-wise, but they're still much slower than a hard drive. And that's only on 2-dimensional media. Add a third dimension, and you get something which is absolutely wonderful for backups, but not for general use.
Though I'll be the first to admit, the day I can use Trek-like "isolinear chips" will be quite cool indeed...
Drives is not a bottleneck. If you need performance, go with RAID.
I can transfer 34 MB/s from my disks (sustained), and around 100 MB/s from my main memory (RAM). As I see it, disks are not the problem here.
RAM today does some sort of parallel-like access to get the performance they get today. If you do the same with you disks, (and why wouldn't you, if performance is that important?) you get equal speedup. Also put more CPUs in your box, when the CPUs become the bottleneck.
Today in PCs, the PCI bus is the only real bottleneck, perhaps along with the memory subsystem. The memory subsystem has improved a lot over the last few years, but the majority of PCs still come with 32 bit 33MHz PCI busses.
When we start seeing motherboards with 64 bit 66 MHz PCI, that's when we'll again be looking at disks, cpus and memory as the bottleneck.
I think there's room for the Solid-state "drives". Which is actually memory, but in harddisk speed and size (several Gigabytes). But it should be cheaper than hard disks (sooner or later ;), and it is already faster.
Actually you can even buy Solid-state drives today, but it costs much, isn't big enough for your bucks...
Can anyone throw in a few URLs?
with the assistance of "Tata Industrial Semiconductors" (name changed for security purposes), a Taiwan based (location changed for security purposes) silicon foundry.
"new Electron Trap design..."
"We may just NOT sell it to the top 10 PC Companies who monopolize our industry."
and my favorite:
"We have no idea where the drawings from which we derived our TCAP came from."
Umm.. aliens, maybe? And put it in a PII shell? Come on.... The whole thing just sounds ludicrous. :-)
Heh, did some more digging, and they *do* claim that the technology came from aliens! :-)
Here's a guy who has some info on their claims, mostly debunking them. http://www.uni-weimar.de/~kuehnel/TrueorNot.htm
Research has been underway for a few years on the "protein drive." The operative principle is a photosensitive protein which occurs naturally in swamps. I believe that it darkens upon exposure to light to cause the (light/dark)-(1/0) memory mechanism. Throughput is proportional to the time required for the protein to respond to the light condition, and storage density is proportional to molecular "resolution" and the energy of the impinging light waves. The storage capacity of the funny-looking-prototypes in the labs in '97 was on the order of 1GB/cm^2. The access time was on the order of 10^-3 s. Improvement should come from tweaking the molecularity of the protein, possibly by mutating the life-forms that produce it (speculation.)
John Mashey (SGI, was MIPS, Bell Labs) has been lecturing recently on "Infrastress" which discusses the problem of computer architecture not keeping up with CPU speed. Not just a problem of slow disks, which can be raided to get parallel speed increases, but bus and net bandwidths, etc. He says: "It's as if cars suddenly became 10 times cheaper, but the roads didn't change." See articles: here and here.
Actually, SCSI drives tend to be quite a bit
faster than IDE drives in their media transfer rate and average seek times. Also, note that the top-end scsi drives now spin at 10Krpm, while IDE is only now getting to 7200. With ATA/66, the interface speed isn't actually all that different.
There is also the point that SCSI can generally queue commands to multiple devices, while ATA is just getting into that.
It's not that SCSI is expensive, it's that IDE is disgustingly cheap since Intel decided to stick it in their chipsets. If they had picked SCSI as the interface-of-choice, we'd all be packing UW storage now, and there'd be people evangelizing about some other format, say Firewire.
Of course, (as mentioned elsewhere on this thread) the point is the actual storage speed, not the interface speed.
-Chris
It's a shame that so many parts of PCs are still made with mechanical parts. And in my experience, those are the ones that fail. The hard drive, floppy drive, plethora of fans, and removable storage of all kinds. And these are all the technologies that "slow us down" on the path to Uber-computerdom. What we need is standardized, solid-state memory devices. Two kinds: a fast one that can be assembled into huge storage devices, and a cheap one that can be used to transfer data between machines. Forget floppies, CDs, Zip disks, and hard drives. We'll have the storage catch up with the memory, cpu, and system bus.
:)
The questions of course are: reliability, performance, and durability. Even using old 30-pin simms in huge arrays attached to a constant power source would probably be faster (overall, not bursting, unless there was a really nice cache on there) than =5400rpm drives, but how long is that going to last? And if you build a twenty-meg portable "disk" out of this, what happens when you drop it on the floor?
Oh well. I think I'll go drool about that atlas 10K now...
-Chris
Just Talking out my ass here, but havent we been hearing great things every now and then about holographic crystal storage? Didn't they want those out within 5 years? I can't remeber.
:)
As a second note, with faster/cheaper/denser ram comming all the time, ram based static hard drives might come to replay magnetic media. (might) I know I want one.
-Crutcher
-- Crutcher --
#include <disclaimer.h>
You can only make a mechanical device operate so fast before the laws of physics start destroying it - or making it prohibitively expensive and large.
If we want to get out of the slow storage days, solid-state mass storage devices will have to become practical for everyone. Or some of the other fancy stuff that only exists in labs right now will have to become a parketplace reality. Hard disks as we know them appear to be coming to the end of their evolution, at least in terms of speed.
There's ongoing research ( http://nanonet.rice.edu/research/boy d_res.html) to use photopolymers as a cheaper holographic medium. If such research comes to fruition, you're more likely to see CD like disks coated w/ a holographic layer than the typical science fiction "data crystal."
Other problems w/ holograms:
- materials are not totally transparent, so "cubes" might be out of the question
-materials must be chemically resistant to the atmosphere (e.g. oxidation, humidity), which might necessitate that they are coated. Such a coating might have deleterious effects on the substrates optical properties.
- storing a hologram changes the structure of the crystal, which can cause limits of data density and beam penetration.
- multiple holograms can be stored at the same location by rotating the crystal, but each hologram attenuates the possible intensity of subsequent holograms in that location.
- holographic "efficency" is a funciton of the difference between the refractive indices of the substrate components. photopolymers have a very small range of refractive indices as oppossed to inorganic crystals.
Overall the medium might not be rewritable, but a high density, long lasting storage medium would be ideal for back-ups.
Anyway, it's been awhile since I "got out of the business" of chemistry, but this is what I remember.
Have you ever seen a harddrive from 1970? I have one. It's has a silver, aluminum case, which is rather odly shaped. It's 6"x5"x"6. And it weighs quite a lot. It has three plastic screwes with heads that are about 3/4" in diamter. The data cable looks like those brown unsheilded, translucent cables that can be found in inkjet printers (the thing connected to the place where you put the ink). It has a capacity of 100MB. It was taken out of an IBM cluster controller (if you know what that is [was]).
Hard Drives have come a long was since 1970. Now CARS. CARS have gone nowhere since 1970.
http://www.spie.org/web/oer/june/jun98/opcwg.html
I read the above link about two years ago, and was amazed by the technology. Quarter-sized 100TB holographic discs. They're supposed to have something viable in another year; here's hoping!
Read: Rabbit Rue - Free serial nove
Basically, the ideal would be to have all computer parts run at core processor speed, but this just isn't goint to happen. We have registers, L1 cache, L2 cahce, (k6-3 L3 cache in some boards), main memory, hard drives...
Sure, it would be ideal for all storage to be as fast as the processor, but the current cached model works pretty well provided you have enough rams and a OS that makes good use of that ram...
If you really need more performance, use RAID...
www.cdrom.com doesn't seem to be disk limited, that's because it has boku memory and raid arrays.
Besides, hard drives today are about 10x as fast (10x more throughput, initial latency has been cut about 4x) as those of 10 years ago, which isn't too bad in machanical engineering terms...
Blessed are the pessimists, for they have made backups.
Here is a web page to check they have basicaly a 90gig solid state hard drive that looks like it could plug into a PII slot one processor slot you would just need a funky mother board or a expansion card I would prefer if it was on the mother board or through and AGP slot for fastest throughput ofcourse they could attack it just like a cpu and get the fastest through put the storagge would run at the same speed as the cpu almost eleminating the need for ram.
http://www.accpc.com/tcapstore.htm
"Never judge a man till you've walked a mile in his shoes. This way when you do you are a mile away and have his shoes."