How is the SSD and high capacity hard drive split on a fusion drive?
iMac Line (2012 and Later)
See if the following article helps answer your question on Fusion drives:
I believe 3T fusion drive contains 128Gb SSD + 3T HDD.
In terms of how the system allocates and utilizes the system - is controlled by Apple engineers' algorithms.
I have used different Fusion drives (with different SSD sizes), even have explored 256Gb(SSD)+256Gb(SSD)= 512GB on my Mac Mini server. I can not really tell the structure of the system/data.
I'm not entirely sure, but part of the SSD is just used as a write cache to temporarily store data you are saving so it happens quickly, then the system will transfer this data from the fast SSD to the slower hard drive.
IIRC macOS will also store the more frequently used files on the SSD so that they open much more quickly.
How any of this is done or regulated is something Apple tends to keep secret. I do know that another user recently posted that macOS reported no more storage space available once the 3TB hard drive was filled so you may not really have HD + SSD as the total amount usable for actual storage. This particular user found that if they kept a bit of free storage space open below the 3TB limit the Fusion Drive setup performed as expected.
Thanks much.
Like for a 3 TB Fusion drive, is something like 500 GB allocated to SSD activities and 2.5 TB to high capacity hard drive, or does the allocation change dynamically depending on demand and disc activity?
Thanks.
Do you mean how do you split it, rejoin a split, or something else?
Very detailed and helpful. Many thanks.
You're very welcome!
How is the SSD and high capacity hard drive split on a fusion drive?
