FileVault slows down USB stick dramatically

Discussion in 'macOS' started by lancastor, May 21, 2016.

  1. lancastor macrumors 6502a

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    #1
    I have read many opinions that FileVault encryption on Mac OS doesn't slows down read and write speed in a big amount.

    I have used BlackMagics Disk Speed Test to compare a fresh formatted stick with and without encyrption.

    Not encrypted stick: Read 55 Mbit/s / Write 132 Mbit/s
    FileFault encrypted stick: Read 29 Mbit/s / Write 77 Mbit/s

    Is this a normal behavior that FileFault dramatically slows down the read and write speed?
     
  2. grahamperrin macrumors 601

    grahamperrin

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  3. lancastor thread starter macrumors 6502a

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  4. grahamperrin macrumors 601

    grahamperrin

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    #4
  5. Weaselboy Moderator

    Weaselboy

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    #5
    I have had the same experience when using FV on USB thumb drives. My theory is the controllers on those things are low end and can't handle the overhead of the encryption. I have tried even supposed "high end" USB keys and they are all horrible with FV turned on.

    What I have done that seems much faster is to make an encrypted sparse bundle image and put that on the USB key, then put any files inside the encrypted image. That seems to keep the speeds up pretty well.

    https://support.apple.com/en-us/HT201599
     
  6. grahamperrin macrumors 601

    grahamperrin

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    #6
    If encryption is not a feature of the drive then to the controller, it's simply data (e.g. blocks); decryption will be performed by the Mac.

    Sparse bundle disk image: smart. I guess that for some USB flash drives, the size of the bands (within the bundle) + OS X = superior (to Core Storage) for performance.
     
  7. Weaselboy, May 21, 2016
    Last edited: May 21, 2016

    Weaselboy Moderator

    Weaselboy

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    #7
    Yes in theory... but you can test it yourself. Format three or four USB keys in encrypted format and I suspect you will find what I did... that the transfer speeds go straight to hell.
     
  8. lancastor thread starter macrumors 6502a

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    #8
    Ok, thanks for the hints.

    I think the spare image solution is a very good way to have both. Encrypted stick and fast bandwidth.
     
  9. grahamperrin macrumors 601

    grahamperrin

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    #9
    I don't doubt that performance can be worse with Core Storage.

    @Weaselboy maybe think of it like this: the USB flash drive can not know whether Core Storage or DiskImages framework or whatever is in use …
     
  10. Weaselboy Moderator

    Weaselboy

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    #10
    Understood... but the data is written to the storage chip differently with core storage and these low end controllers found in USB keys just don't seem to be able to deal with that.
     
  11. grahamperrin macrumors 601

    grahamperrin

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