Capacities and Hella Overprovisioning

SandForce’s attention is focused on the enterprise, which makes sense given that’s where the money is. As a result, its drives are aimed at enterprise capacity points. The first products you’ll see based on SandForce will be 50, 100, 200 and 400GB capacity points. That’s in GB, in terms of user space it’s 46.6 GiB, 93.1GiB, 186.3GiB and 372.5GiB.

On top of the ~7% spare area you get from the GB to GiB conversion, SandForce specifies an additional 20% flash be set aside for spare area. The table below sums up the relationship between total flash, advertised capacity and user capacity on these four drives:

Advertised Capacity Total Flash User Space
50GB 64GB 46.6GB
100GB 128GB 93.1GB
200GB 256GB 186.3GB
400GB 512GB 372.5GB

 

This is more spare area than even Intel sets aside on its enterprise X25-E drive. It makes sense when you consider that SandForce does have to store more data in its spare area (all of that DuraWrite and RAISE redundancy stuff).

Dedicating almost a third of the flash capacity to spare area is bound to improve performance, but also seriously screw up costs. That doesn’t really matter for the enterprise market (who’s going to complain about a $1500 drive vs. a $1000 drive?), but for the client space it’s a much bigger problem. Desktop and notebook buyers are much more price sensitive. This is where SandForce’s partners will need to use cheaper/lower grade NAND flash to stay competitive, at least in the client space. Let’s hope SandForce’s redundancy and error correction technology actually works.

There’s another solution for client drives. We’re getting these odd capacity points today because the majority of SF’s work was on enterprise technology, the client version of the firmware with less spare area is just further behind. We’ll eventually see 60GB, 120GB, 240GB and 480GB drives. Consult the helpful table below for the lowdown:

Advertised Capacity Total Flash User Space
60GB 64GB 55.9GB
120GB 128GB 111.8GB
240GB 256GB 223.5GB
480GB 512GB 447.0GB

 

That’s nearly 13% spare area on a consumer drive! Almost twice what Intel sets aside. SandForce believes this is the unavoidable direction all SSDs are headed in. Intel would definitely benefit from nearly twice the spare area, but how much more you willing to pay for a faster SSD? It would seem that SandForce’s conclusion only works if you can lower the cost of flash (possibly by going with cheaper NAND).

Controlling Costs with no DRAM and Cheaper Flash Inside the Vertex 2 Pro
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  • fertilizer - Tuesday, January 05, 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?
    Reply
  • j718 - Tuesday, January 05, 2010 - link

    the ocz vertex ex is an slc drive, not mlc as shown in the charts. Reply
  • j718 - Tuesday, January 05, 2010 - link

    whoops, sorry, it's just the anandtech storage bench charts that have the ex mislabeled.
    Reply
  • Donald99 - Monday, January 04, 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.
    Reply
  • cliffa3 - Monday, January 04, 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?
    Reply
  • MadMan007 - Monday, January 04, 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) Reply
  • vol7ron - Monday, January 04, 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
    Reply
  • vol7ron - Monday, January 04, 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
    Reply
  • Guspaz - Sunday, January 03, 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.
    Reply
  • kunedog - Monday, January 04, 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.
    Reply

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