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.'"

Comments

Prehistory? Depends on context

[Hentai]

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.

Personally, I can't wait until it comes out...

[HoneyBunchesOfGoats]

...'cause that means prices will drop on hard disks that I can use.

Re:too bad that

[Magila]

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.

Re:too bad that

[ltwally]

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 :)

IDE TROLLS: READ THIS

[darkwiz]

SCSI drives are notorious for their noise, heat and vibration levels. These low points are not acceptable at the consumer level. Noise and heat don't matter too much in huge server rooms, but they can quickly become a problem in desktops.

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.

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).

Re:SCSI?

[G-funk]

it's got nothing to do with how common it is, scsi is expensive because it raises the percieved value of the product, and it's common knowledge that this "elite"ness of more expensive alternatives to a product aid sales.

In short, it's expensive because they like it that way. There's no shortage of scsi drives, they're not particularly more expensive to produce.

Re:SCSI?

[GooberToo]

Someone mod this guy up. He, "gets it!" SCSI is expensive because it's the premium, top-shelf product. Period. SCSI is expensive for the same reason that diamonds are. Both are highly desired but have no more value than the next drive (be it IDE or rock).

In other words, they are expensive because people want to keep them that way!

Re:SCSI TROLLS: READ THIS

[mosch]

That has nothing to do with SCSI. The only reason it's even remotely related is because people have a tendancy to buy SCSI drives like this one, which is a 15K RPM drive with a 3.2ms seek, and the ability to sustain a 75MB/sec data throughput rate, whereas high-end ATA drives like this one spin at 7200 RPM, have a 9ms seek, and don't list their maximum sustained data throughput rate on the data sheet.

Is IDE appropriate for the desktop? absolutely.

Will retards continue using IDE in applications where SCSI is far more appropriate? definitely.

Does your post make any fucking sense at all? nope.

Am I missing something here???

[Lobsang]

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...

SATA propagates all the crap of PATA

[mnemotronic]

Serial ATA has kept all the truely horrible, obscure, and performance limiting features of parallel ATA (which was originally designed for 40 Mbyte drives), and shoves it down a thin cable. A course in ATA protocols will leave anyone who is computer literate going : You have got to be kidding!! What were they smoking????? The Serial spec has to maintain all kinds of bizarre, obsolete behavior just so that a SATA drive is backwards compatible with old software (i.e. that WfWG 3.11 system you've got tucked away in the closet). Throughout the history of ATA, when drive capacities climb towards the addressable limit of the spec, the protocol is kludged by a team of drunken baboons to extend it for another generation. The SATA committee munched an opportunity to drill a much-needed stake through the heart of ATA and give us a new interface for the next 20 years. Instead we get a change in connectors for a protocol with it's feet firmly encased in the concrete of MS-DOS 2.

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".