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SATA 3.0 Release Paves the Way To 6Gb/sec Devices
An anonymous reader writes "The Serial ATA International Organization (SATA-IO) has just released the new Serial ATA Revision 3.0 specification. With the new 3.0 specification, the path has been paved to enable future devices to transfer up to 6Gb/sec as well as provide enhancements to support multimedia applications. Like other SATA specifications, the 3.0 specification is backward compatible with earlier SATA products and devices. This makes it easy for motherboard manufactures to go ahead and upgrade to the new specification without having to worry about its customers' legacy SATA devices. This should make adoption of the new specification fast, like previous adoptions of SATA 2.0 (or 3Gb/sec) technology."
Devices which aggregate themselves as a striped array behind a single eSATA/SATA interface. While the individual device may not be able to pump out enough data, they can in aggregate.
Wow, both your numbers are wrong. SATA 2.0 has a theoretical transfer rate of 3Gb/s, not 3GB/s. It also uses an 8b/10b encoding, so 3.0Gb/s translates to 300MB/s. Data throughput will be less than that, thanks to control protocol overhead, though the overhead is very small.
Modern drives do seriously better than 25MB/s. Seriously, go look at benchmarks. Also, SSDs, which are a very real design influence on things like SATA, are already getting close to the 300MB/s mark.
1.21 Joule Watts?
WTF is 1.21 m^4*kg^2/s^5 good for?
You do realize that at either end of a Parallel link you'd have to re-serialize right? That's what PATA does. So you still need the high clock rate regardless of how much you parallelize it on the wires. That's extra hardware, and another piece the needs to be be really fast. Then you also have issues with maintaining clocking integrity over parallel lines, which gets tricky at high data rates.
Right now, our technology is better in going pure serial. In the past, it was parallel. It might swing back and forth a couple of times between the two in the future. But make no mistake: right now, on commodity hardware for drives connected via cables, serial is pulling ahead in the speed war.
The problem with parallel is that you can't crank up the clock speed because you have to make sure that the signal on each line is combined with the ones from the other lines that were sent at the same time. This limits how fast you can send the send the bits (if the time being bits is comparable to the skew time, the receiver will not be able to reliably reassemble the data) and how long the interconnect can be (skew being linearly amplified by length). It's not for nothing that PCI has been replaced with PCI-E, PATA with SATA, SCSI with SAS. USB and IEE1394 would be impossible with parallel. Serial communications are more reliable and more scalable (one big exception -- wireless RF, but that's not what we are discussing here).
Multiprocessing, incidentally, has nothing to do with it -- the software interface to a storage device hides all the implementation details (PATA/SATA, for instance) anyway. The hard part in multi-threading IO-intensive apps has quite a bit more to do with latency issues and atomicity guarantees (the complete lack thereof) rather than the inability of the storage device to do 2 things at once (which, for a physical disk, is impossible anyway, meaning that it would have to back-convert into a serial process anyway).
If my understanding of the technology is correct, the seek time on most hard drives already limits drive access speed to typically be slower than 3Gb/sec. Would this rely on a transition to Solid State Drives for any noticeable difference in performance?
The seek time has nothing to do with the throughput. The seek time refers to the latency between when a read command is issued and when it begins to be fulfilled. The throughput refers to the data transferred per unit time during fulfillment.
Here's a nice car analogy for those of us in New England -- consider the Mass Pike versus I-93. The Mass Pike has a very long seek time from the onramp because of the toll lanes (and the mouth breathers that won't get a transponder even though they are now free and clog the automatic lanes) but once you get on the highway, you can go 80 MPH until your exit. On I-93, by contrast, you can get right on, but you will be going 30 MPH for the duration. Of course, if you drive down to CT and get on I-84, you have a low-latency AND high throughput highway but if you drive too far down to, say, the Bronx, it becomes high-latency and low throughput.
Sequential reads on large-capacity drives are often in the 70-90MB/s range (yes MB, not Mb), bursting into the 200MB/s range. Hell, I've seen 50MB/s+ for at least the last half a decade. High-quality (read: expensive) SSDs can roughly double that.
And of course, the spec is in gigabits per second, not gigabytes, and includes overhead. Actual supported, sustained transfer is supported at 150MB/s, 300MB/s, and 600MB/s on SATAI-III respectively.
How are sites slashdotted when nobody reads TFAs?