lexikhan
Posts: 1
Joined: Thu Aug 23, 2012 8:21 pm

Faster SD card writing for OSX (and possibly linux)

Thu Aug 23, 2012 8:31 pm

Most instructions I've found for using dd to copy the Raspbian (or other linux) image onto the SD card use a 1m block size or not setting it at all. I found that by changing the block size to 32768 (32K) the write speed increased by more than 80x. The full command would be:

dd bs=32768 if={path/to/raspbian.img} of=/dev/{yoursdcarddevice}

Except replace the parts in { } with your appropriate information.

JonB
Posts: 220
Joined: Tue Nov 29, 2011 9:26 pm

Re: Faster SD card writing for OSX (and possibly linux)

Fri Aug 24, 2012 7:59 am

I'm trying this with a PNY 4Gig Class 4 card. I observe no increase in speed - what type of card are you using?

I'm getting ~800k/sec on write.

woutervanwijk
Posts: 10
Joined: Mon Jan 21, 2013 12:35 pm

Re: Faster SD card writing for OSX (and possibly linux)

Mon Jan 21, 2013 12:36 pm

I get the best results with 1M. Your solution is faster on my computer than no blocksize, but slower than 1M

efflandt
Posts: 359
Joined: Mon Dec 03, 2012 2:47 am
Location: Elgin, IL USA

Re: Faster SD card writing for OSX (and possibly linux)

Tue Jan 22, 2013 2:41 am

I have been using bs=4M because that is what Debian recommended for writing regular PC Linux images. I have never timed it. Speed might depend upon whether the card has been written to before or how often, because flash memory has to erase blocks to all 1's before it can clear bits for any that are 0's. Although, they wear level by writing new data to different less used blocks when possible.

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