bit-tech.net

SATA-IO announces 16Gb/s SATA 3.2 specification

SATA-IO announces 16Gb/s SATA 3.2 specification

SATA 3.2 introduces SATA Express, boosting the maximum theoretical throughput for storage devices from 6Gb/s to a whopping 16Gb/s.

SATA-IO, the industry group behind the Serial ATA standard, has formally released the SATA 3.2 specification with the promise of boosting transfer rates as high as 16Gb/s in future devices.

The latest revision of the long-running SATA specification, SATA 3.2 brings a number of improvements for storage devices - but by far the most interesting is SATA Express. A variant of SATA first announced back in January this year, SATA Express uses up to two PCI Express 3.0 lanes to offer a peak transfer rate of 16Gb/s, or 2GB/s, compared to SATA 3's 6Gb/s.

To visualise the performance difference, it's easiest to fall back on the old Blu-ray comparison: a SATA 3 storage device capable of saturating the 6Gb/s bus speed would transfer a 50GB Blu-ray image in around 67 seconds; a storage device running over SATA Express, meanwhile, could do the same in just 25 seconds.

Naturally, you need your storage device to keep up with the performance of the bus: most current SATA 3 devices struggle to reach anywhere near the 6Gb/s theoretical limit, with most solid-state drives (SSDs) peaking somewhere around 4.8Gb/s at best. The exception is in high-performance RAID arrays of multiple devices, which are becoming increasingly popular in the enterprise as first-line non-volatile storage for databases and other performance-critical files.

While SSDs that connect directly to a PCI Express bus already exist, the SATA 3.2 standard is about compatibility: a host compliant with the specification, SATA-IO explains, will be able to address storage over PCI Express or traditional SATA transparently. The group does, however, predict a future in which solid-state mass storage is exclusively connected via SATA Express over PCI Express, with traditional SATA ports being used purely for low-performance mechanical and optical drives.

SATA 3.2 isn't just about increased speed, however. The new specification also brings support for the Next Generation Form Factor (NGFF) defined by the PCI Special Interest Group (PCI-SIG). Now known as M.2, the ultra-compact cards will include the option of SATA connectivity for use as a storage form factor alongside Wi-Fi, WWAN, USB and PCI Express capabilities.

The specification also includes the micro-SSD standard for embedded storage devices, a slimmer variant of the Universal Storage Module (USM) form factor, a new ultra-low power device suspension level dubbed DevSleep, transactional energy reporting for better power management, a system for better controlling the data caching system on solid-state hybrid drives (SSHDs) and a feature for speeding up the process of rebuilding a RAID array.

'SATA technology continues to evolve to accommodate ever-changing storage industry requirements,' claimed Mladen Luksic, SATA-IO president, at the specification's announcement. 'The updates featured in the revision 3.2 specification, such as SATA Express and enhancements for emerging solid state hybrid drives, are driven by current market trends. These new features demonstrate SATA-IO’s ongoing commitment to providing low-cost, high-performance storage solutions.'

9 Comments

Discuss in the forums Reply
schmidtbag 13th August 2013, 16:05 Quote
Couldn't they have just stepped it down to about 14Gb/s and not use 2 lanes? Also, does that mean it requires 2 lanes per SATA port, or 2 lanes for an entire set of ports (presumably 4 or 6 per set)? If it's the latter, I think it's dumb they use 2 lanes because that means you can't buy a 1x slot card, and it's a real waste of a 16x slot.
Gareth Halfacree 13th August 2013, 16:09 Quote
Quote:
Originally Posted by schmidtbag
Couldn't they have just stepped it down to about 14Gb/s and not use 2 lanes? Also, does that mean it requires 2 lanes per SATA port, or 2 lanes for an entire set of ports (presumably 4 or 6 per set)?
There are no ports: SATA Express connects via a PCI Express slot, not a SATA port. This isn't an HBA they're talking about: a SATA Express drive would be a bunch of NAND flash strapped to a PCI Express card. Basically, exactly what we've got now in PCIe SSDs but 'talking' SATA so the OS doesn't have to give a monkey's how the drive it's communicating with is connected.
schmidtbag 13th August 2013, 16:14 Quote
Quote:
Originally Posted by Gareth Halfacree
There are no ports: SATA Express connects via a PCI Express slot, not a SATA port. This isn't an HBA they're talking about: a SATA Express drive would be a bunch of NAND flash strapped to a PCI Express card. Basically, exactly what we've got now in PCIe SSDs but 'talking' SATA so the OS doesn't have to give a monkey's how the drive it's communicating with is connected.

Ah ok. I understood the idea of the PCIe card but I guess I was picturing more that there would also eventually be standard SATA ports that operate at 16Gb/s.
azazel1024 13th August 2013, 17:05 Quote
One thing to point out on the article, there are plenty of SSDs that saturate the bus. SATA 3.0 is theoretically capable of 6Gbps, or 750MB/sec. However, SATA overhead imposes a limit closer to 550-575MB/sec. There are a number of SSDs that are capable of this today.

It is "easy enough" with a moderately large SSD to easily exceed the limits on SATA3.0, all you have to do is expand how many channels the controller uses. There are no hard an fast limits on this, other than most SSDs use 8 channels because they are already saturating the SATA3.0 link...so why use more?

Moving to SATA3.2 and SATA Express with a 16Gbps limit means that manufacturers can easily move to 12 or 16 channel controller designs for their SSDs and bump the speeds by a fair margin. I doubt we'll have to wait more than 2-3 years before SATA Express is maxed out by the fastest SSDs.

The other thing this helps with is random performance and access times. SATA has a good sized overhead added on top of what the controller and NAND itself is actually capable of. I'd be suprised if this didn't increase performance by a good percentage in random access times and things like random 4k I/O...which are what needs improvement more than high sequential transfer speeds.

Keep in mind, most PCI-e SSDs currently work using a PCI-e bridge chip. It is SSD controller that either "speaks" SATA on the output side, or else it works with an SATA controller and then is connected to a PCI-e bridge chip and then connected to the machines PCI-e controller. So it is STILL working through SATA. SATA3.2 however removes that. You are connecting directly to the PCI-e controller without a bridge chip and the controller on the SSD is speaking PCI-e effectively (or at least it is extending SATA over PCI-e from what I understand of it).

Since it is all working native PCI-e...even though it is speaking SATA over it, it removes a HUGE amount of the delays and overhead of the SATA bus.

This is a lot more than simply increasing max theoretical bandwidth to 16Gbps. It is also about reducing I/O bottlenecks, random performance, new form factors, reducing power consumption and heat.
Elton 13th August 2013, 20:11 Quote
That's actually a rather impressive idea. SataE probably won't take off that quickly. But the PCI-e solution is now much more elegant than beofre.
iwod 14th August 2013, 10:27 Quote
The problem i see, is that by the term the industry moves forward with SATA-Express 16Gbps, the speed of NAND with 8 Channel would have surprised the Interface Speed again. Since PCI-E 4.0 isn't even ready yet why cant we move straight to 4x PCI-E interface?
azazel1024 14th August 2013, 15:39 Quote
Likely the next spec will. Since this is basically SATA extended over the PCI-e interface, it is maxed out at 4xPCI-e 2.0. I am a little befuddled as to why it doesn't work over PCI-e 3.0 and uses the slower standard, but it is what it is.

I'd imagine it would be a (relatively) minor process to revise/update the spec at a future date to have it take advantage of PCI-e 3.0 and a future 4.0 for large speed boosts.
ch424 14th August 2013, 20:25 Quote
It might just be that PCIe 3.0 is much harder/more expensive to implement than PCIe 2.0.

PCIe Gen 2 was basically just a speed bump up from PCIe 1, and not much else changed. PCIe 3.0 has a completely different physical layer and the speed bump up to 8GT/sec pushes it over the edge of what you can do "easily" in digital silicon. PCIe 2.0 at 5GT/sec is 2.5GHz, which we're used to seeing in chips the whole time. To get your PHY running at the 4GHz you need for 8GT/sec gen 3 takes much more effort, and probably adds costs that you don't want in an SSD controller that costs a few $.
FeAr3d 17th February 2014, 22:22 Quote
I would love to see sata ports, both on the mb as well as esata, deliver power and not just data so i don't need to plug in extra power lines to SSD's, HDD's and ODD's.
Thanks!
Log in

You are not logged in, please login with your forum account below. If you don't already have an account please register to start contributing.



Discuss in the forums