I have a late 2014 27" iMac that I run off a 2TB Samsung SSD using a Seagate Thunderbolt 2 sled instead of the internal drive. It's a heck of a lot faster than the internal Fusion drive.
I thought of breaking the Fusion drive into a 128gb SSD for the OS and most used apps and using the spinning drive for data. Any recommendation on that setup. Has anyone done it or seen any data on it? Will it be just as fast as the external SSD?
It sounds like a good idea, but real-world speeds for many common tasks may actually be very close. You could do your own benchmarks with a drive utility. The Thunderbolt 2 SSD should be pretty fast, and I am not exactly sure of the specs of your particular PCIe internal blade SSD, but they may be fairly close. There may be some slight advantage to splitting up the OS and your apps and data on two different drives on their own interfaces, since you can use both at the same time. Install the OS on both and time how fast it boots from each one. Launch apps, open a large document. Copy/Paste to duplicate a large movie file. Do your own real world tests. I think the theoretical specs of the Thunderbolt 2 might be a little faster, but if you are searching over a smaller 128GB Volume on that blade SSD, compared to a larger 2TB Volume, the PCIe might actually be a little faster, for some tasks.
No.
You missed the point. Will breaking the Fusion drive into a 128gb SSD for the OS and most used apps and using the spinning drive for data be faster than the current setup of an external SSD for booting and storage?
It's fairly common but really there is no reason to break the Fuse between the SSD and the HD. Simply re-format the Fusion drive to erase it and then use it for additional storage and you should be fine.
Late 2014 27" iMac drive setup
