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SD Card Questions



  • In the past, I have stuck to using Samsung EVO 32GB SD cards for the most part. I use a usb external hard drive to hold my ROMs, saves, and the lot with my Retropie base install on the sd card.

    With the release of the RP4, I have been rethinking my choice and am curious of a few things.

    It appears the RP4 now has a 50MB/s transfer rate. With SD cards, reading and writing have different speed caps.

    Is the Pi SD hardware limited by any such factor?

    If not, I need to upgrade my card to some such as a Sandisk Extreme to benefit going forward as the EVO 32 only has a 20 MB/s write capability. I know the 64GB has a faster write speed but don't need to backup an image that is 64GB in size with 80% of it being unused space.

    Is there a program that will create an image backup and eliminate free space ?

    This would be useful on any size card for me as I enjoy using my USB hard drive even though it adds a second box to my setup. I find it easier to manage as my primary computer is a Windows laptop. I do dual boot windows with Slackware on my school laptop and have Mint on my main home laptop as I've been trying to utilize those OSes more and gain better knowledge. If I could get a 16gb card I'd do that honestly but the price points for these card is just getting stupid now as I got a 32GB Evo Select for $5.49 USD today on Amazon. I never saw the need for anything better since the Pi was capped and writing a full backup to a card was pretty much never happening.

    Just curious how others manage their systems and whatnot especially with the RP4 having better specs in this department now.


  • Global Moderator

    @KN4THX said in SD Card Questions:

    Is there a program that will create an image backup and eliminate free space ?

    Pishrink is what you need - https://github.com/Drewsif/PiShrink.



  • @KN4THX You could also first use a 16 or 32 gb sd card to build your image. The software automatically expands the file system to the maximum capacity when you insert the card for the first time. Then you back up your image and then when you write the image to a 64 gb card it will stay at 16 / 32 gb. So unless you need the extra space, you can keep the size at 16 / 32 gb and will have backups of the same size.



  • @BobHarris Thanks, that's an idea to consider. I think I'm going to try PiShrink like @mitu suggested and see how that works out and go from there.



  • @BobHarris This is exactly what I did too. When my Pi 3 build was under heavy "development", I used 16 gb sd card. The backups took only 16 minutes and 16 gb each time (sometimes multiple times every day). When I was ready, I flashed the image to a 64 gb model, where I have much slower backup and progress rate.

    But with the Pi 4 I will go back to 16 gb sd card + external small factor usb 3.0 500 gb hard drive (which I have left over currently).



  • @thelostsoul Are you going back to the external drive because of the USB 3 upgrade?



  • @KN4THX I wanted that before Pi 4 was announced, the separation of OS is my goal. I need more space and hard drives are faster, cheaper and more fail safe (in theory) compared to sd cards. The USB 3 upgrade comes just right. In the future I plan to replace the hard drive with a ssd. Upgrading to different size is no problem and the main OS on sd card stays small.



  • @thelostsoul I thought about going the SSD route but standards drives are so crazy cheap I can't bring myself to do it for an external drive yet. I would LOVE to have a solid state drive though just for the bumps and bangs when I travel with my Pi though so maybe with the 4 coming out I'll reconsider that.



  • @KN4THX Exactly. I wouldn't buy a ssd drive just for a Pi, but when I upgrade the ssd on my main pc, then I could use the older one.



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