MacBook Pro – Increasing Write Speed to MicroSD on macOS

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I am experiencing really slow write speeds on my MacBook Pro on a MicroSD from Samsung which should allow write speeds of up to 20MB/s. The current transfer rate seems to be around 3-4MB/s on HFS Journaled, and the rate was way lower when I formatted it with exFAT. I see some methods for increasing speeds on other devices like Android mobiles, which involve changing the cache, and also on OSX but only for command line processes? Is there a way to implement this when dragging files over with Finder?

Best Answer

Indicated write/read speeds are always higher than what you should expect from a card.

Usually, the filesystem doesn't make a difference to the RW speeds.

Do also remember that copying many small files is significantly slower than copying one big file due to the entries required to the FS.

If you'd like to test your write speeds with the filesystem, try

dd if=/dev/zero | pv -betrP -s 100M -S | dd of=/path/to/your/device/temporaryfile

The above command will dd 100 mebibytes of zeros into a file into your microSD card, and will return a speed in MiB/s.

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