SandForce’s Achilles’ Heel

I surmised that SandForce’s DuraWrite technology would only be able to reduce the number of flash writes on data that was easily compressible. Documents, libraries, executables, as evidenced by the Windows 7 + Office 2007 install achieving a very low write amplification of 0.44x.

To see how bad the drive’s performance would suffer if we dealt primarily with compressed files I created a test that exclusively copied compressed files to the drive - MP3s, JPGs, x264s, RARs and DivX movies. I wrote roughly 20GB of compressed data to the drive and measured average IOs per second and disk bandwidth.

Processor Average IOPS Bandwidth
OCZ Vertex 2 Pro 100GB 241 IOPS 145.9 MB/s
OCZ Vertex 256GB 181 IOPS 181.5 MB/s
Intel X25-M G2 160GB 110 IOPS 109.9 MB/s

 

While the Vertex 2 Pro achieves a competitive average IOPS, its effective bandwidth is actually lower than the older Indilinx based Vertex SSD. What this tells us is that some of those write requests took much longer to complete on the Vertex 2. It’s akin to having two video cards with the same average frame rate, but one with a much lower minimum frame rate.

I wouldn’t characterize its performance as unacceptable by any means. Remember this is pre-production hardware and it’s still faster than X25-M G2 thanks to Intel’s ~100MB/s write limit. What it does show however is a weakness in the DuraWrite technology. Presumably the majority of your file writes aren’t going to be compressed files so your performance shouldn’t be gated by this issue, even then I’ve shown that you shouldn’t be any worse off than you would be with Intel’s X25-M.

AnandTech Storage Bench Final Words
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  • fertilizer - Tuesday, January 5, 2010 - link

    First of all, my complements to a great article!
    It provided me with great insight!

    It seems to me that SSD manufacturers are spending a lot of time complying to the world of HDD based Operating Systems.
    Would'nt it be time to get OS's to treat a SSD differently than a HDD?
  • j718 - Tuesday, January 5, 2010 - link

    the ocz vertex ex is an slc drive, not mlc as shown in the charts.
  • j718 - Tuesday, January 5, 2010 - link

    whoops, sorry, it's just the anandtech storage bench charts that have the ex mislabeled.
  • Donald99 - Monday, January 4, 2010 - link

    Any thoughts on potential energy use in mobile environment? Compared to intel MLC. Still better energy efficiencey than a traditional drive?
    Performance results seem uber.
  • cliffa3 - Monday, January 4, 2010 - link

    Anand,

    Great article, will be an interesting technology to watch and see how mature it really is.

    Question on the timeline for the price drop: When you said 'we'll see 160GB down at $225', were you talking about the mid-year refresh or the end of year next-gen?
  • MadMan007 - Monday, January 4, 2010 - link

    Is it just me or is it inaccurate to mix GB and GiB when calculating overprovisioning at the bottom of page 5? By my reckoning the overprovisioning should be 6.6% (64GB/60GB, 128GB/120GB) not double that from using (64GB/55.9GiB etc)
  • vol7ron - Monday, January 4, 2010 - link

    Anand, the right column of the table should be marked as GiB.

    The last paragraph should take that into consideration. Either the second column should first be converted into GiB, or if it already is (and hard to believe it is), then you could do direct division from there.

    The new table:
    Adv.(GB) Tot.(GB) Tot.(GiB) User(GiB)
    50 64 59.6 46.6
    100 128 119.2 93.1
    200 256 238.4 186.3
    400 512 476.8 372.5

    The new percentages should be:
    (59.6-46.6) / 59.6 x 100 = 21.8% decrease
    (119.2-93.1) / 119.2 x 100 = 21.9% decrease
    (238.4-186.3) / 238.4 x 100 = 21.9% decrease
    (476.8-372.5) / 476.8 x 100 = 21.9% decrease


    And the second table:
    Adv.(GB) Tot.(GB) Tot.(GiB) User(GiB)
    60 64 59.6 55.9
    120 128 119.2 111.8
    240 256 238.4 223.5
    480 512 476.8 447

    The new percentages should be:
    (59.6-55.9) / 59.6 x 100 = 6.21% decrease
    (119.2-111.8) / 119.2 x 100 = 6.21% decrease
    (238.4-223.5) / 238.4 x 100 = 6.25% decrease
    (476.8-447) / 476.8 x 100 = 6.25% decrease


    Note, I did not use significant figures, so all numbers are approximated, yet suitable - the theoretical value may be slightly different.


    vol7ron
  • vol7ron - Monday, January 4, 2010 - link

    Anand, the right column of the table should be marked as GiB.

    The last paragraph should take that into consideration. Either the second column should first be converted into GiB, or if it already is (and hard to believe it is), then you could do direct division from there.

    The new table:
    Adv.(GB) Tot.(GB) Tot.(GiB) User(GiB)
    50 64 59.6 46.6
    100 128 119.2 93.1
    200 256 238.4 186.3
    400 512 476.8 372.5

    The new percentages should be:
    (59.6-46.6) / 59.6 x 100 = 21.8% decrease
    (119.2-93.1) / 119.2 x 100 = 21.9% decrease
    (238.4-186.3) / 238.4 x 100 = 21.9% decrease
    (476.8-372.5) / 476.8 x 100 = 21.9% decrease


    And the second table:
    Adv.(GB) Tot.(GB) Tot.(GiB) User(GiB)
    60 64 59.6 55.9
    120 128 119.2 111.8
    240 256 238.4 223.5
    480 512 476.8 447

    The new percentages should be:
    (59.6-55.9) / 59.6 x 100 = 6.21% decrease
    (119.2-111.8) / 119.2 x 100 = 6.21% decrease
    (238.4-223.5) / 238.4 x 100 = 6.25% decrease
    (476.8-447) / 476.8 x 100 = 6.25% decrease


    Note, I did not use significant figures, so all numbers are approximated, yet suitable - the theoretical value may be slightly different.


    vol7ron
  • Guspaz - Sunday, January 3, 2010 - link

    Your pricing estimates for Intel's refreshes worry me, and I worry that you're out of touch with SSD pricing.

    Intel's G2 x25-m 160GB drive currently sells for $500-550, so claims that Intel will be selling 600GB drives at the same price point raise some eyebrows.
  • kunedog - Monday, January 4, 2010 - link

    I couldn't help but roll my eyes a little when I saw that Anand was again making Intel SSD pricing predictions. Even the G1 X-25Ms skyrocketed above his predictions for the G2s:
    http://www.anandtech.com/storage/showdoc.aspx?i=36...">http://www.anandtech.com/storage/showdoc.aspx?i=36...

    And the G1s are still higher at Newegg (the G2s are still a LOT higher). Anand has never acknowledged the stratospheric X-25M G2 pricing and how dead wrong his predictions were. He's kept us updated on negative aspects like the firmware bugs, slow stock/availability of G2s, and lack of TRIM for G1s, but never pricing.

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