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6 Gb/s SATA: Seagate’s Barracuda XT And Marvell’s SSD Controller

6 Gb/s SATA: Seagate’s Barracuda XT And Marvell’s SSD Controller
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I still remember Intel’s Developer Forum in 2008, before the company had launched its Core i7 ‘Bloomfield’ lineup on LGA 1366.  All of the demo machines Intel was showing off behind closed doors were driven by its then-unreleased SSDs. And I still remember Francois Piednoel noting that, without SSDs, the performance of Core i7 would be handicapped by conventional hard drives. Since then, we’ve tied solid state storage into as much of our high-end processor and graphics testing as possible.

As you no doubt already know, hard drives and SSDs alike have almost universally connected to the rest of your system via 3 Gb/s SATA ports. The standard has been fairly accessible since 2005, so most remotely-modern machines already support it.

Three gigabits per second divided by eight gives you a maximum throughput of 375 megabytes per second. However, 8b/10b encoding exacts an immediate 20% bandwidth penalty, dropping the ceiling of a single SATA 3 Gb/s port to 300 MB/s. That’s actually a fairly large pipe. It’s large enough, in fact, that no single mechanical hard drive is able to saturate it (Patrick has an upcoming review of Western Digital’s 2TB Caviar Black where it pushes about 140 MB/s in sequential reads). It takes a current-generation SSD performing sequential reads to hit the limits of what SATA 3 Gb/s can do. And even then, we’d hardly call the latest drives bottlenecked by their SATA interface.

Yet, here I sit, staring at an Asus motherboard with Marvell’s 88SE9128 6 Gb/s SATA controller, Seagate’s behemoth 2TB Barracuda XT 6 Gb/s SATA drive, and an engineering sample of Marvell’s upcoming 6 Gb/s SSD controller.

And when I say engineering sample, I mean very, very early hardware. As in, this SSD sports a single-digit serial number and doesn’t include any NAND flash memory. Thus, we’re only able to test the controller itself using a limited number of benchmarks. I can't even include a picture of the thing's guts without raising hell.

I don’t have time to do a formal review of the Asus motherboard or the Seagate drive (my flight to Spain leaves in 10 hours). Thomas will be taking care of Asus' P55-based P7P55D Premium motherboard soon, and Patrick plans to cover the Barracuda XT in an upcoming feature. Today, I’m able to offer a quick look at how these three components work together and a brief peek at performance.

Update: It's worth noting that, with 600 MB/s possible per SATA 6 Gb/s port, the P55's second-gen PCI Express links (limited to 2.5 GT/s each) are really insufficient. Asus gets around this on the P7P55D Premium with a PLX8613 second-gen bridge chip, which takes four of the PCH's links and turns them into a single 500 MB/s connection to Marvell's SATA controller. In theory, there's still a potential bottleneck there. But as we'll see, even today's storage devices are really quite unable to saturate it.

A First Look At SATA 6 Gb/s

Before we start playing with Marvell’s latest controller, let’s have a look at the first 6 Gb/s SATA hard drive to hit our labs: Seagate’s Barracuda XT. The 2TB monster spins at 7,200 RPM and sports a 64MB data buffer, similar to Western Digital’s Caviar Black (though the 2TB Caviar is limited to 3 Gb/s signaling).

Because it supports SATA 6 Gb/s transfer rates, Seagate is able to claim a maximum interface speed of up to 600 MB/s—twice what SATA 3 Gb/s could do. Of course, it’s wholly unrealistic to expect the drive to come anywhere close. It boasts the same areal density and similar raw data rates as the Barracuda 7200.12s we benchmarked earlier this year; performance should be, for the most part, fairly similar.

In order to zero in on any gain enabled by the 6 Gb/s interface, we tested the Barracuda XT on Marvell’s 88SE9128 and then again on Intel’s P55 PCH, with write-cache buffer flushing enabled and disabled in both environments.


Write-Cache Buffer Flushing Enabled
Write-Cache Buffer Flushing Disabled
6 Gb/s Marvell Controller
5495
6420
3 Gb/s Intel P55 Controller
5307
6045


In PCMark Vantage, two things are apparent. First, there’s a significant performance improvement to be had when you disable Windows write-cache buffer flushing (it’s enabled by default), and second, regardless of whether you have the aforementioned feature turned on or off, the 6 Gb/s interface helps Seagate’s Barracuda XT out a bit.


6 Gb/s Marvell Controller
3 Gb/s Intel Controller
Sequential Read Performance
138.5 MB/s
138.5 MB/s
Random Access Speed
17.12ms
17.13 ms


We get the same sequential read throughput and read access results in H2benchw.

Everest Ultimate Edition

6 Gb/s Marvell Controller
3 Gb/s Intel Controller
Linear Read (Beginning)
140.1 MB/s
140.1 MB/s
Linear Read (Middle)
113.8 MB/s
114.5 MB/s
Linear Read (End)
64.4 MB/s
64.4 MB/s
Random Read
101.7 MB/s
73.3 MB/s
Read Access
16.64 ms
17.05 ms
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  • 4 Hide
    themadmanazn , October 23, 2009 9:27 AM
    Nice article, looking forward using this technology in a few years =)
  • -3 Hide
    cyberkuberiah , October 23, 2009 12:27 PM
    we want usb 3 , sata 3 and pcie 3 by mid 2010 as mainstream features !
  • 0 Hide
    cyberkuberiah , October 23, 2009 12:36 PM
    32nm lynnfields of tomorrow should have 16 lanes but of pcie3 , so that x8 pcie 3.0 crossfire becomes comparable to x16 pcie 2.0 crossfire of today , as mainstream , because just to buy a quality motherboard with dual x16 2.0 means at least $70+ more in intel compared to 790fx+sb750 motherboards . pcie3 was due but got delayed , i sceptically wonder why .
  • 0 Hide
    huron , October 23, 2009 3:52 PM
    I was looking for SATA 6Gb/s and USB 3.0 on my next motherboard. I hear there are some in the works for next year. I look forward to this being more common sometime in the near future.
  • 9 Hide
    WheelsOfConfusion , October 23, 2009 5:32 PM
    Trips to Spain, constantly upgrading home theater setups, filling your NAS until you need an overkill solution, we get it Chris, you're filthy rich. >:p 
  • 0 Hide
    dcuccia , October 24, 2009 12:47 AM
    Not sure I totally understand...does the Marvell controller support RAID? Couldn't you bandwidth test RAID0 configurations with the Intel G2 drives?
  • 1 Hide
    belardo , October 24, 2009 1:41 AM
    I WANT IT!!!

    My next mobo MUST have:
    SATA 3.0 6GB/s and USB3.0... PCIe 3.0 would be a bonus.
  • 0 Hide
    DjEaZy , October 24, 2009 4:01 AM
    ... it's a blast... the question is... when it will be getting on the mainstream...?
  • 0 Hide
    avatar_raq , October 24, 2009 11:32 AM
    I would like to see a comparison between ASUS Maximus II Extreme (x58) and P7P55D Deluxe SATA III controllers to see if the P55 one truly has a bottleneck affecting the drive performance.
  • -1 Hide
    cangelini , October 24, 2009 1:46 PM
    WheelsOfConfusionTrips to Spain, constantly upgrading home theater setups, filling your NAS until you need an overkill solution, we get it Chris, you're filthy rich. >


    Hah, I wish! Just fortunate to be able to work with some cool people and cool hardware. First real vacation since my honeymoon almost five years ago!
    Cheers from Barcelona!
    Chris
  • 0 Hide
    cyberkuberiah , October 24, 2009 2:05 PM
    BelardoI WANT IT!!!My next mobo MUST have:SATA 3.0 6GB/s and USB3.0... PCIe 3.0 would be a bonus.


    yes and thank god nobody flagged your comment as negative ... i wonder what sort of elitist junta flagged me red for same demands ... and mid 2010 is full 8 months away !
  • 0 Hide
    cyberkuberiah , October 24, 2009 2:12 PM
    ok , i get it , people want it earlier than that ? even better , let's keep our fingers crossed !
  • 0 Hide
    MRFS , October 24, 2009 2:43 PM
    There are PCI-E RAID controllers available now with
    SAS/6G support e.g. Intel's RS2BL080 and RS2BL040:

    http://www.intel.com/Products/Server/RAID-controllers/RS2BL080/RS2BL080-overview.htm
    http://www.intel.com/Products/Server/RAID-controllers/RS2BL040/RS2BL040-overview.htm

    The "SATA/6G" solution on the ASUS P7P55D Premium is not
    truly "6G" because it has a bottleneck at PCI-E x1 Gen2
    (250 MB/sec x 2 in one direction):

    http://www.supremelaw.org/systems/asus/PCIe.x1.Gen2.jpg
    (archived for "fair use" purposes: see source below)

    = max headroom of 500 MB/second, not 600 MB/second.

    Latter limitation is described in more detail here:

    http://www.pcper.com/article.php?aid=769


    The Intel RAID controllers above do not appear to have
    that limitation. If I understand the Marvell controller
    described in this article, a good test would be to wire
    it to one of the Intel RAID controllers above and
    "let 'er rip" :) 


    MRFS
  • 0 Hide
    belardo , October 28, 2009 9:55 AM
    Does seem stupid to say "yeah! Cool! I want #####"...

    oh well.
  • 1 Hide
    Anonymous , October 30, 2009 4:23 PM
    Chris, have fun in Spain!