Dual Port SAS SSDs

Discussion in 'Hard Drives and Solid State Drives' started by redeamon, Nov 2, 2019.

  1. redeamon

    redeamon Member

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    Hey Folks,

    I'm getting a bunch of Dual Port 12gb/s SAS SSDs with read performance of 1.9GB+/sec. How does one get this level of performance from SAS3 via dual port? Are there any controllers out there that support "performance" dual port? I know on some platforms dual port is used for redundancy but are there any that utilize dual port for performance?
     
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    Last edited: Nov 2, 2019
  2. Spartacus

    Spartacus Active Member

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    So if I'm interpreting your question correct, depending on the cable/controller most support 4 lanes, so SAS 3.0 is 4x 12Gbit/s which is about 4.8GB/s total throughput or in the case of dual port 2x 12Gbit/s or 2.4GB/s which exceeds your 1.9GB/s ask.
    There aren't many SSD I'm aware of pushing the 4.8GB/s limit even on the U.2 level, hence why most backplanes/expanders use it for redundancy rather than performance, its not really needed.
     
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  3. redeamon

    redeamon Member

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    I might be wrong, but I don't think SAS3 pushes 4 lanes to each device. It seems that each device gets 1 lane- so roughly 1500mb/sec (theoretically). In real life I've never seen over 1gb/sec on any SAS3 SSD. Maybe I'm doing something stupid or my systems need tuning? All my Dell r630's have expanders so that plays a factor, but I've done direct connections via a LSI 3008 and it's still capped around 950mb/sec.

    Any ideas?
     
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  4. Spartacus

    Spartacus Active Member

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    You’re correct, was just saying each cable can do that throughput technically, so a true dual lane device/cable should be able to do 2400Mbit/s (likely closer to 2k realworld).

    Not sure on the R630 limit or specifics.
     
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  5. redeamon

    redeamon Member

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    I see. I'll look into cables then, that sounds right.
     
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  6. azev

    azev Active Member

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    to use both sas port on dual port ssd you have 2 options;

    1. Use dual port backplane
    2. Use SAS cable with dual port such as this

    After you figured out the physical topology you need to make sure you have a software that supports SAS MPIO like Windows servers or any linux variance.
     
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  7. David Smith

    David Smith New Member

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    Dual lane port should be able to do this..... agree with @azev
     
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