John Galea's Blog

My blog on Gadgets and the like

64G Sandisk uSDXC card review

A while back I bought one of these cards on ebay and I have no idea whether the card was defective or what but I had no end of issues with it. So this time around I was uber paranoid when working with it.

The first thing you need to know is any cards beyond 32G are a new standard called SDXC. Your device may or may not support it. This includes card readers, cameras, phones, tablets etc. Before you buy one of these cards be sure you can use it.

As with any flash card the first thing I like to do is run a thorough test of the card using H2Testw. What this does is write a unique pattern to the entire card and then read/verify it back off. This confirms the card is the size it says it is and that it is not defective. There have been waves of fake cards on ebay. It will also tell you the speed of the card.

This particular one got 14MB/s write and 41 MB/s read. The card is a class 10 so this is in line with what it ought to get. Each class is good for 1MB/s so a class 10 ought to get 10 MB/s as a minimum.

The card came formatted as eXFAT. While fine for Windows some versions of Android can’t read it. Happily my S3 with Android 4.1.2 can read eXFAT. A welcome surprise! If yours can not you will need the dos format command with the option /fs:fat32 and don’t forget the /q or your in for a long wait to format the card. And I mean REALLY long. Almost 2 hours. I know cause I forgot the /q :). Interestingly after waiting over 2 hours Windows 7 informed me the card is too big for FAT32 and failed to format it. Guess it’s good that the S3 supports ExFAT. The S3 can even format the 64G and does so with ExFAT as the default. It created the drive with 128K allocation size. A little wasteful when my 32G card had an allocation size was 16K. By comparsion my 30G of content consumed 421M more with the larger allocation unit. With the 4K allocation size the same content occupied 38M less.

I played around with allocation size and measured performance. I tried it at 4K, 16K, 128K and 1024K and it made little difference. At most it made 7% difference with the larger block size being faster. 128K was the fastest. So for the sake of saving space, cause every bit counts, I am going to go with 16K ExFAT, almost as fast and reasonable data waste. (Raw data was 4K 31733, 16K 33920, 128K 34009, 1024K 33870 all are MB per sec measured using Checker).

My Samsung Galaxy Tab 2 7 GT-P6210 running Android 4.04 does not support ExFAT so won’t work with the 64G 😦 My Samsung S2 I727R running Android 4.1.2 did support exFAT!

Here’s the Wikipedia article on eXFAT. One of the main benefits of exFAT for me is breaking the age old barrier that FAT32 has, a max file size of 4G. This is problematic for hidef 720/1080p movies. Yay, at last a solution! NTFS is still not supported on Android 4.1.2 on my S3, sadly. And permissions are not supported on Win 7 on eXFAT. Not an issue when the card will be used in Android but still worth noting.

So that`s about it. I finally almost a year later have a 64G card working in my phone, all ready for more content! Is there ever enough 🙂



April 19, 2013 - Posted by | Android


  1. Brief and right on the point. Thank you!

    Comment by Sergey | March 29, 2015 | Reply

    • Thanks Sergey! Come back often, tell your friends 🙂

      Comment by johngalea | March 30, 2015 | Reply

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