One of the lower-key innovations Apple introduced yesterday was the new Fusion Drive introduced in the new redesigned iMacs. Apple’s website outlines how the new technology works:
With Fusion Drive in your iMac, disk-intensive tasks — from booting up to launching apps to importing photos — are faster and more efficient. That’s because frequently used items are kept at the ready on speedy flash storage, while infrequently accessed items go to the hard drive. The file transfers take place in the background, so you won’t even notice.
Many, including myself just thought that this was Apple’s branding of a hybrid drive, which uses an SSD as a caching system, but this does not appear to be the case. The MacObserver has some of the details.
To be clear, this is not a caching concept, at least not in the current use of the word. Cache would imply that the data on the SSD is duplicated, and it’s not. If you have a 1TB mechanical drive paired with the 128GB SSD, you have a 1.12 TB storage platform. This truly is the fusion of all the space on two separate disks.
In other implementations of similar features, files that exist on the hard disk are temporarily mirrored onto the SSD for faster speeds. In Apple’s implementation files are actually moved from the hard disk to the SSD.
The report wraps up by saying that the two separate drives appear as one logical partition, this means if the hard disk fails, it could be replaced and the new drive could be used with the Fusion technology as well. The Fusion drives will be an option for both the new iMac and Mac mini when they become available.