In OSX, SD Card transfers can be painfully slow

Over the weekend, I was trying to experiment with some SD card images for the
UDOO Board.

When copying a new image into my SD Card, I realized that I was getting a really
ridiculous slow writing speed of 1MB/s. This means that an 7GB image will take
100+ minutes just to copy.

It didn’t feel right with me and doing some quick googling, I’ve found out that
if I’m doing a ‘dd’ directly to /dev/diskX which is where the sdcard is normally
mounted, I’ll be subjected to this slow speed.

What I should had done is to dd to /dev/rdiskX instead.

The reason being is that /diskX is buffered in 4KB chunks. Meaning that a copy
to diskX will be buffered 4KB at a time. This slows down speeds massively.

Source:

Apple FileSystem Mailing
List

Apple.Stackexchange