SD card used for an SSD

Discussion in 'iMac' started by zarathu, Aug 3, 2011.

  1. zarathu macrumors regular

    zarathu

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    May 14, 2003
    #1
    This may have been asked before but a search didn't find it.

    What are the advantages or disadvantages of plugging an SD card(32gb or 64gb) into the side of the iMac and using it for an SSD drive?
     
  2. simsaladimbamba, Aug 3, 2011
    Last edited: Aug 4, 2011

    simsaladimbamba

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    #2
    Even the fastest SD card will be slower than a conventional HDD, thus you will not have any SSD-like experience.
    13
     
  3. zarathu thread starter macrumors regular

    zarathu

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    #3

    Of course.... but how much faster than a 7200 hard drive?
     
  4. AdrianK macrumors 68020

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    #4
    You mean slower?
     
  5. iLidz macrumors member

    iLidz

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    #5
    Wirelessly posted (iPhone 4: Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8G4 Safari/6533.18.5)

    The advantage of a bootable SD card is portability. You can carry your OS, Apps and documents in your pocket.

    The disadvantage, as has already been stated, would be speed. The SD card will be nothing like an SSD Speed wise and will be will slower than a XXXX ( pick a speed, it doesn't matter) RPM HDD.
     
  6. xraydoc macrumors demi-god

    xraydoc

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    #6
    Quoted for emphasis.
     
  7. zarathu thread starter macrumors regular

    zarathu

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    #7
    So you are saying that acess to the card would be slower than ANY HARD DRIVE?
     
  8. xraydoc macrumors demi-god

    xraydoc

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    #8
    Yes. SD cards are not designed to have the performance levels of a dedicated SSD.

    Even if they somehow could, the card reader is a USB 2.0 device (400Mbit/sec max.) while a dedicated SSD is going to be running off the SATA 2 interface (3Gbps/sec).
     
  9. zarathu thread starter macrumors regular

    zarathu

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    #9
    Thanks for your kind and knowledgeable response.
     
  10. atopos, Aug 3, 2011
    Last edited: Aug 3, 2011

    atopos macrumors newbie

    atopos

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    #10
    What about 45MB/s cart (SanDisk Extreme Pro)
    with the hypothetical dedicated Thunderbolt reader ?
    Still slow ?
     
  11. Stan Mikulenka macrumors 6502

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  12. 88 King macrumors 6502

    88 King

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    #12
    Completely agree. Top range class 10 64Gb even some 32GB SD card from major manufactures cost the same or more the cheapest 64GB ssd. So why would you pay more and settle for USB performance? Just buy a cheap 64GB ssd and run it via Firewire.
     
  13. Icaras macrumors 603

    Icaras

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    #13
    And you're back to square one again. Theres's no point in getting an SSD when you're going to run it through Firewire since it doesn't have the bandwidth to take advantage of the SSD. If you're going to go firewire, you're better off getting a 7200RPM HDD which will not only be far far more cheaper, but will also have vastly more space.

    Only connect SSD with Thunderbolt.
     
  14. zarathu thread starter macrumors regular

    zarathu

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    #14
    Where can you purchase a dedicated Thunderbolt reader? The point here is not to use it for your entire HD, but for some selected things such as storing photos in Aperture that you need very quick access to.
     
  15. simsaladimbamba, Aug 4, 2011
    Last edited: Aug 4, 2011

    simsaladimbamba

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    #15
    Still slower than a 5400RPM HDD, except with access times.

    Still hypothetical, thus non existent.

    7
     
  16. coolspot18 macrumors 65816

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    #16
    A traditional hard drive's can sustain ~80 - 100MB/s.


    Also not sure what the lifespan of the SD card would be like if there are a lot of writes tot he card. Flash memory has a finite number of reads/writes.
     
  17. gentlefury macrumors 68030

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  18. Weaselboy Moderator

    Weaselboy

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    #18
    Although FW does not fully exploit the speed potential of a SSD, there are many forum posts here from users who put a SSD in an external FW 800 enclosure and see much better speed and system responsiveness than with an internal HDD. SSD in FW 800 external is a very viable alternative.
     
  19. coolspot18 macrumors 65816

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    #19
    The card is only rated for 45MB/s... 90MB/s is marketing speaking. Also, UHS cards may require a UHS enabled card reader to take advantage of the speed.
     
  20. Icaras macrumors 603

    Icaras

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    #20
    I'm sure there are speed improvements that would warrant it as a viable alternative, but I think it's value is greatly diminished by bottlenecking the SSD through a slower interface. The speed increases are probably slight and I don't think it's worth splurging the money over.
     
  21. stevendphoto macrumors member

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    #21
    Ever watch the news?
     
  22. blackNBUK macrumors 6502a

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    #22
    I think that concentrating solely on the bandwidth available is a mistake. This is only one factor in the overall performance of a disk drive. The seek time (i.e. the time it takes to find the data you need) can be just as important if not more so. For example booting a computer involves accessing lots of small files that maybe scattered across your drive. In this situation seek time will be a major factor in how long the whole process takes.

    Seek time is one area were SSDs are vastly better than HDDs, which isn't surprising when you consider that a HDD has to physical move heads around to access your data. It is also one area where the limited bandwidth of Firewire is not going to be a problem.

    If anyone is interested this wikipedia article goes into the complexities of comparing SSDs and HDDs.
     
  23. apw100 macrumors regular

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    #23
    First of all, what do you plan on using this drive for?
     
  24. sth macrumors 6502a

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    #24
    Memory cards, even fast ones, are not optimized for high IO loads and thus will be very slow. Their controllers are only optimized for low power consumption and linear reads/writes. For SSD controllers, it's quite the opposite.

    Not entirely correct. It is limiting, but the main reason why SSDs feel so much faster is not the linear read speed. It's the low access time that makes them fast. When reading non-sequential data, HDD speeds quickly drop to a fraction of their theoretical maximum because of the access times.
     
  25. RWil85 macrumors 6502a

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    Aug 2, 2010
    #25
    all this technical jibber-jabber is great. can't we all just agree that this is a silly idea? :rolleyes:
     

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