Mac storage basics · Disks, APFS and formats

What is a Fusion Drive, and does it change how I manage storage?

Q: What is a Fusion Drive, and does it change how I manage storage?

A Fusion Drive, found in some older iMacs and Mac minis, combines a small SSD with a large hard drive and presents them as one disk; macOS keeps frequently used files on the SSD part. Free-space advice is the same, but because most data sits on the slower hard drive, an external SSD can make a noticeable speed difference for apps and projects on these Macs. Don't split the Fusion Drive's parts unless you know exactly what you're doing.

Short answer: A small SSD and a large hard drive combined into one disk on some older Macs. Manage space the usual way; an external SSD can noticeably speed up apps and projects there.

A Fusion Drive, found in some older iMacs and Mac minis, combines a small SSD with a large hard drive and presents them as one disk; macOS keeps frequently used files on the SSD part.

Free-space advice is the same, but because most data sits on the slower hard drive, an external SSD can make a noticeable speed difference for apps and projects on these Macs. Don't split the Fusion Drive's parts unless you know exactly what you're doing.

Last reviewed October 1, 2026

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What is a Fusion Drive, and does it change how I manage storage?

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