Serial ATA Technology Explained
Mike Parsons writes "Explosive Labs has an interesting article on Serial ATA . Here is a quote: 'In the rapidly moving computer industry, there are rarely the kinds of revolutionary changes like what is about to take place in secondary storage segment. Soon the hard drives and configuration methods that have existed since the origins of the personal computer will change forever. The basic IDE technology has been around for nearly twenty years. When the lifetimes of other computer components like CPUs and video are measured in months, twenty years ago seems like prehistory.'"
Think about this - how long has RS232 been defined? How long has the PC's parallel (i.e., LPT1) pin-out been defined? How long has the VGA pin-out been defined? How long has the PC keyboard pin-out and protocol been defined? A lot of things change pretty fast; a lot of things stay around forever. It all depends on whether upgrading them is worth the cost in the long run.
-Hentai [in vita non pacem est]
All of IDE's shortcomings are fixed by SCSI (except for a small degree of added complexity). SCSI hardware is more expensive, and rarely does it come built-in to motherboards.
If more people used it, it would be a cheaper solution, and would fix all of IDE's problems without re-inventing the wheel--it's a solution that, right now, works.
15k rpm scsi drives get seek times in the low three range--that's three times faster than your average 5400 rpm ide hdd.
Slashdot: Where people pretend to be twice as smart as they really are by behaving like children.
So...why don't we use firewire? Isn't it faster than SATA? And the upcomming Firewire IEE 1394b should double the firewire speed to ~800mb/s. And let's not forget the fact that there are firewire HDD-s and other perhipeals on the market (though they are generaly external) or maybe, could this have anything to do with INTEL's desire to controll all components? I don't see the price as a limiting factor either.
Live for the present, learn from the past, and dream of the future!
The author then goes on to note that the 'roadmap' calls for the 2006 version to run at 600mb/s, which fits nicely with my roadmap to world domination in 2005. ...Ummmm, yeah, we'll see.
Although looking at the list of upcoming products and the manufactures making them, I don't doubt we'll all be useing this in a few years.
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis
...'cause that means prices will drop on hard disks that I can use.
Since the site is slashdotted, here are further links about Serial ATA:
Cnet
SATA and ISCSI
Intel Dev Paper
Maxtor White Paper
This sounds remarkably like the plugs we got for Rambus RDRAM: serial interface is better than parallel, first gen won't see real performance gains, stick with us kids, this is gonna be really good.
I see a decided lack of Sun, IBM, AMD, or HP listed in the adopters, which leads me to believe that this is much like the above. Sorry guys, I'm not riding the first wave of any new tech on my salary. I'll sit on the sidelines for awhile and see how this pans out.
Wu-Tang Name: Half-Cut Skeleton Get your own Wu-Na
For the time being, IDE isn't going anywhere.
NOISE & HEAT will tend to outweigh (relatively) minor performance gains in consumer systems. (Enterprise hardware is another matter entirely)
sigh....we need to start using those annoying javascripts that make people read the article BEFORE posting.
When in doubt, parenthesize. At the very least it will let some poor schmuck bounce on the % key in vi. (Larry Wall)
All data goes through the PCI bus
No it doesnt. Data goes through the PCI bus if the address is not claimed by something else along the way. That means that everything from the southbridge up is not limited by the PCI bus bandwidth. That means that integrated SATA controllers (not available until next year) are only limited by the bandwidth between the northbridge and southbridge.
Ever read the actual throughput specs on a drive?
Drive throughput has been steadily increasing, and it is predicted to pass up PATA within a few years, and that is not counting RAID striping or the 8 MB drive caches. Its always desirable for the bottleneck to be the drive rather than the controller.
"The defense of freedom requires the advance of freedom" - George W Bush
Personally, I could give a rats butt about the speed. I don't want SATA so my drives go faster. I want it so I'm not having to spend twenty minutes doing finger gymnastics everytime I need to do _anything_ in my case.
Is it worth upgrading for? No, probably not. But id damn sure is worth waiting an extra few months for that next machine to save the hassel of those f'ing ribbon cables.
jello.
aka aron.
Why are they wasting their time on this ancient technology? Serial is too slow to sync my damn Palm Pilot. I can't even imagine what it would be like to try and transfer 60GB of media files over it. These companies should just accept that USB is the way of the future (no extra power required either!) and get to work on something that stands a chance of selling.
Karma: Good (despite my invention of the Karma: sig)
What on earth does the type of interface have to do with heat or noise?
Yes- but AFAIK command queuing is not implemented in a lot of the 1st generation controllers because it can break backwards compatibility with PATA software. Most vendors went for an easy upgrade path instead. Look for command queuing in the next generation of controllers.
"The defense of freedom requires the advance of freedom" - George W Bush
4 of them in RAID 0?
This won't be an issue since SATA is strictly point-to-point, every drive gets it's own 150MB/s link.
I don't get it ... I quite agree that, as a serial bus, it'll be clocked a lot faster than IDE ... but a simple back-of-the-envelope calculation tells us that it has to be at least 8 times as fast as the current devices (it'd have to be 533 MHz to be on par with ATA-66)
It looks like a technology whose main purpose is to make things incompatible, and thus require people upgrade more stuff. And anyway, it's not the speed of the bus the limiting factor (for the vast majority of users), but the mechanics of the harddrive (SCSI hardrives are faster than IDEs because they almost always are top-of-the-line products with higher rotational speeds - anybody saw a 15000 RPM IDE ?)
The Raven
The Raven
For starters, the PCI spec isn't limited to 133 MB/s. PCI 2.1 specs allow for 66 MHz 64-bit transfers, which equals 528 MB/s. PCI 2.2 specs allow for PCI-X mode, which adds 133 MHz 64-bit transfers: 1056 MB/s.
:)
That being said, it is entirely possible to reach throughputs in excess of 133 MB/s using a PCI bus... though currently most desktop motherboards do not support anything faster than 133 MB/s. In time this will change as NICs, hard disks, and other gear requires it.
And your hard disk performance is barely par by today's standards. IDE drives are currently topping 50MB/s, while SCSI gear is hittin > 70MB/s. Though I am a SCSI man, i can see the future need for SATA. Right now it may be mainly a marketing ploy... But in a couple years it will be a necessity. Parallel cabling is nearing the end of the road.. all those wires in a cable allow for too much signal interference. Serial is the answer. Though it has less wires, the dramatic increase in signal strength allows for insane transfer rates.
Anyhoo.. personally I don't see any reason to go out and buy a new system just to have SATA. At the current it offers few advantages.. but in the not so distant future it will be a necessity for desktop systems. As for me, i plan on going Fibre-Channel SCSI
/dev/random
Absolutely. But this has nothing to do with SCSI, it has to do with the high spindle speeds at the bleeding edge. The card on the underside of the drive is not making that ear shattering racket. They even acknowledge that in your quote.
SCSI is better than ATA. Even SATA. ATA has been trying to catch up by stealing some of the best parts of SCSI (like TCQ). But it just isn't quite as good yet. Quite frankly, I agree with the majority of SCSI zealots: if the damn PC makers would embrace SCSI, then the cost of SCSI would come down to near parity from the volume of sales.
Now, is SCSI better for your average Joe? Maybe not significantly. Neither is 7200 vs 5400, 2MB vs 8MB buffers, or 8.9 vs 9.1 ms access times.
However, if they could use one cable to connect 15 devices in their tower, they'd be alot happier than having the 8 cables they'd need to do it with current IDE tech (let alone IDE's relative inability to be used externally).
Note that almost all the Firewire hard drives that you see on the market are ATA hard drives with FirewireATA hardware in the enclosures. As far as I'm aware, the only disks that you can readily get your hands on will have interfaces of IDE/ATA, SATA, SCSI (of various connectors), and FC-AL. That's why you can't use Firewire inside a PC. Using SATA makes far more sense, especially for migrating to a new standard, as it's most likely easier to make a SATAATA adapter since the protocol is very similar.
This post is an *excellent* example of what watching too much super-fast cutting TV (like MTV) can do to you.
I think I am. Really.
The article seems immensely biased and lacking in technical detail. It also raises some "dubious" points IMHO. Let's see:
- P-ATA cables cannot be longer than 40cm. S-ATA cables can be up to 1m long:
Granted, those cables are annoying. But really, how many times have you felt the need for a cable much longer than 40cm? People with full-sized cases may benefit, but then the author says that the current trend is "small footprint machines". So, why do I need a cable that is bigger than my server?
Also, if you dislike flat cables, buy "rounded" P-ATA cables (available today, just google for it).
- P-ATA connectors are big!
Yes, they are! But you'll require at least twice as many S-ATA connectors, as only one device is supported... In the end, the real state on the mobo is going to be similar.
- One device per controller is an "Advantage".
C'mon... This guy must be joking. I couldn't believe my eyes when I read it! One device per controller is an *advantage*???? Why??? I wish I could add more devices (like SCSI and Firewire) to my curreny P-ATA technology. And then he says ONE is good for me? Don't think so...
- High transfer rates are useful for multi-disk RAIDS.
What kind of RAID? RAID 5 is slow in writes due to the computational power needed to calculate the XOR. Adding bandwidth won't help. And I can't see why or how only RAIDs will benefit from higher throughput.
- Speed:
Granted. It may be faster than P-ATA. But what about established technologies like SCSI and Firewire? I *think* (not sure) Firewire can go much faster than S-ATA in its initial version.
I'm disappointed...
Firewire (1394) was killed by Apple's licensing fees and Intel's sudden backstabbing policy change on building it into south-bridge, along with their NIH attitude. There existed working 1394 Device Bay drives over 6 years ago, with OS support from m-soft. 1394 was an attempt to keep the good parts of SCSI protocol, while leaving out as much of the useless stuff as possible (MODE SELECT).
Fibre-channel is still Real Pricey, for the same reason that SCSI is -- "just because". Or, as the hardware vendors say "harrumph, well, it's all about volume".
The Russians have won. They have made the world a cesspool of distrust, greed, fear and hate.
It's real simple, ribbon cables SUCK, they cost more to make then serial so PC makers hate them.
So, here's how it is...
Fibre Channel - 2Mb/s(10Mb coming very soon), 126 drives, 10+ mile range, better then SCSI.
S-ATA - 1.2Mb/s(2.4Mb in 2004), 18" range?, IDE protocols for all your write-only data needs.
S-ATA is the Ghetto FibreChannel, just like IDE is crappy SCSI, expect similar suckiness and low quality to go with the low price and cheaper cables (to make, to buy they will cost more I'm sure).
But again, this is all about the creaper cables, since lets face it 95%+ of the machines out there only have one drive anyway.
- Adam L. Beberg - The Cosm Project - http://www.mithral.com/
Please, for the love of everything that's geek... DON'T use "drop" and "hard drive" in the same sentance.
1. You can't HOTSWAP an IDE drive without risking blowing your drive, crontroller, or upsetting the powersupply.
With SATA you can.
2. You can't WARMSWAP an IDE drive, without risking blowing your drive, controller, or upsetting your powersupply.
With SATA you can.
3. IDE still only supports 2, yes 2 drivers per controller, which makes it impossible to do hardware RAID-5. That leaves us with software RAID-5 as our only option.
Who cares when you can get hardware RAID-controllers with 12 ports on one card? What is the great advantage of having the cable be the single point of failure for your whole RAID, like SCSI does?
4. IDE cables can only stretch so far, so even if you could somehow manage to get 8 IDE controllers into a box, for a total of 16 drives, there would still be cable length issues. I think 1 m is max. We need differential IDE :)
Ok, 1m can be a problem for some people. However most people do not have cases larger than 1m.
5. IDE drives are just now able to verify data integrity, but thats good since we can start using IDE drives in servers that don't need 100% uptime.
Err, why is it a problem when it is already fixed as you say?
6. ATA/100 Round IDE cables are already available. In fact I just ordered some that have a UV reflective coating for my next case mod which features a black light. Airflow isn't a big issue, in fact Compaq has been slicing up IDE cables for a long time now to increase airflow.
Round IDE-cables are expensive to produce and still large and inflexible. SATA solves it.
7. The SUSTAINED TRANSFER WRITE RATE of IDE drives is still not fast enough to store uncompressed NTSC video at 60 frames per second, or store high bandwidth Satellite streams.
So get the hardware RAID-controller and start streaming away. Oh wait, hardware RAID for SATA doesn't exist. 3ware is a figment of my imagination.
8a. Size increase (GB's) are not keeping pace with read/write access speeds and simply adding cache RAM and tweaking seek algorithms isn't going to remedy this problem.
You can't blame the interface for that. 150MB/s per drive for 12 drives on one card is way more than any SCSI solution supports -- and way more than current drives need.
8b. As, internal volatile write caches grow larger, the risk of uncommitted writes being lost in a power outage or crash increases.
So turn off the write cache. ATA supports Transaction Command Queueing although not all drives support it yet. By the time SATA drives become available, TCQ should be common.
Finally! A year of moderation! Ready for 2019?