Crazy Memory usage on Transcend 128GB JetDrive 130 Expansion Card for MBA I've just received my new JetDrive Lite 130 designed for Macbook Air. When I plugged it in, I was happy to see 128GB available on the empty card. However, I copied 16GB of files to it and the Finder now tells me only 89.3GB is available. That's 39GB less space for 16GB of usage! The folder itself shows 16m bytes and 25GB on disk, whereas on my ssd, it shows 16m bytes and 16GB on disk.

Has anyone else any experience of the same happening? I can understand some additional memory being used up, but 250%!!

I've also heard not to reformat these cards because there are speed optimisations applied during the factory formatting. Is this true?

I've emailed Transcend support anyway, so I'll post their response when I hear back.
As mentioned in my original question, the SD Association (of which Transcend are a member) cite performance impacts as a reason against using standard drive formatters. 

However, they have a formatter available for download at https://www.sdcard.org/downloads/formatter_4. On Mavericks, I reformatted my drive using this utility and recopied my files.

The results were as follows:


A single file 14.57GB took 4 minutes to copy. This is the exactly as advertised 60MB/s write speed.
80k files (16GB), however took 92 minutes to copy. which reflects about 5MB/s


In both cases, however, the info window was as expected showing a reasonable amount of memory usage and memory remaining. So, this solved my original problem.

As a comparison, I decided to reformat as a Journaled and found the following:


14.57GB file took 10 minutes to copy, which is only about 50% of the advertised max speed.
80k files (16GB) more importantly took only 10.5 minutes.


For me, sticking with a Journaled format is a no brainer, particularly if writing lots of small files, which I will be. It also may allow me include this on a Fusion drive, although I haven't investigated this yet.

TL;DR - It is probably best to reformat to a Journaled partition as it provides a more consistent write speed of about 30MB/s, no matter the file sizes. ExFAT ranged between 5 to 60 MB/s speeds, depending on the number of files being written (lower number is faster).

UPDATE: Transcend replied to recommended a replacement.