I just created a "Fusion Drive" on my MacBook Pro by following "How to make a Custom CoreStorage Drive in OS X".

It was created with a 256GB SSD and 320GB HD, with the SSD set as the "primary" disk in the logical volume. However, I'm not seeing much of a speed increase, and I'm not sure my data is being stored to the SSD.

How do I confirm that most of my data is stored on the SSD within a Logical Volume?

I was hoping I could simply see disk usage for each disk within the logical volume, but it looks like diskutil cs list doesn't report that.

2 Answers 2


iostat command check out the complete article from JollyJinx blog.


  • 2
    Whilst your answer may theoretically answer the question, it would be preferable to include the essential parts of the article in an answer below, and provide the link for reference.
    – Pfitz
    Commented Nov 28, 2012 at 15:32

Based on jollyjinx's articles, I made this script which I used to help me test my DIY Fusion setup: https://gist.github.com/11522980

Basically, you have to fill the SSD with garbage files until they flow onto the HDD, then repeatedly access files from the HDD while watching disk activity. Eventually the HDD activity will stop and SSD activity will continue (or start), meaning the files have been effectively transferred.

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