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Discussion in 'macOS' started by mentaluproar, Jan 13, 2013.
How does fusion drive work if you aren't supposed to completely fill an SSD?
What you're not supposed to do is fill your system/boot drive. In the case of a fusion drive, it's the combined space of the SSD and HD you don't want to fill.
So the OS knows to leave room on the SSD?
To rephrase with a fusion drive it doesn't matter where the free space is just as long as you don't fill it when it's the boot drive.
Without free space, how does garbage collection work?
I am not sure what you read where or are really asking about, but I think you're worried over nothing.
I'm not worried so much as curious.
The SSD reserves space internally for garbage collection, block reallocation etc. This is why they come in sizes like 120 or 240 gb instead of 128 or 256 - those two sizes already have 8gb and 16gb inaccessible to the user, and allocated for GC and re-allocations already. Enterprise class drives tend to have more reserved.
Some people like to maintain MORE free space thinking that they can let the SSD have more blocks for this, but it is not required.
It remains to be seen how effective that practice is, as the SSD already has a set amount reserved whatever you do with the device.
in short: you can't entirely fill an SSD and screw up the GC, etc - because the drive doesn't let you see all the space on the physical device.