fusion drive and multiple user accounts

[mogens]

How does core storage handle multiple user accounts. E.g. two users that access different stuff on the fusion drive. Will the user that uses the computer most get all the benefits, or will corestorage start moving files around from the SSD to the HHD every time a new user log in? If that's the case the drives really gonna have a hard time.

 

[simon.hibbs]

How does core storage handle multiple user accounts. E.g. two users that access different stuff on the fusion drive. Will the user that uses the computer most get all the benefits, or will corestorage start moving files around from the SSD to the HHD every time a new user log in? If that's the case the drives really gonna have a hard time.

Core Storage is a base operating system component so it won't be user account aware. Fusion Drive is a block level technology and doesn't even work at the file level, so it won't even be aware of things like file ownership or permissions.

What this means at a practical level is that the most commonly used data, regardless of user ownership, will end up on the flash drive. If both users frequently use the system but one user is responsible for say two thirds of the data read/write activity in the system, then their data will end up on roughly two thirds of the flash drive.

Bear in mind that in this scenario the other user would still end up with about 40 GB of their most used stuff on the flash drive, which is no small amount. Most people only regularly access a small proportion of their total stored data. Also a lot of stuff such as OS components, drivers, application files and such are likely to be frequently accessed by both users so they would both benefit equally from accelerated access to that.

To drive all of the other user's stuff off flash they'd have to read/write well over 100 GB of applications and data before the other user comes along again.

Simon Hibbs

 

[mogens]

Thanks that make sense