School me on Apple's Fusion Drive

[PliotronX]

More specifically, why doesn't it seem to be working as intended on my HR lady's iMac? They have a 120GB SSD and 3TB spinner "fused." Using iostat, there is so little activity on the SSD when running applications that her husband uses all the time (Adobe products, he is a photographer), it leads me to believe that the SSD is used purely only as OS component storage. It has just been lagging at various times.

Before they drive four hours to the nearest Apple store, would it be worth plopping in a larger SSD and installing a fresh El Capitan?

 

[Hellhammer]

Where exactly is the lag happening? Photo editing can be limited by a number of different components depending on the task. E.g. major edits on high quality photos or batch editing are likely to be CPU bound, rather than storage.

Fusion Drive is essentially tiered storage, meaning that the most frequently accessed files are kept in the SSD. That includes the OS components and frequently used apps and files. Basically Fusion Drive learns as it goes, so a photo that was just transferred to the machine won't be in the SSD, but if that same photo is opened for a number of times it will be transferred to the SSD tier for faster access.

 

[tweakboy]

Could be RAM, but that's a long shot,,,

 

[PliotronX]

Where exactly is the lag happening? Photo editing can be limited by a number of different components depending on the task. E.g. major edits on high quality photos or batch editing are likely to be CPU bound, rather than storage.

Fusion Drive is essentially tiered storage, meaning that the most frequently accessed files are kept in the SSD. That includes the OS components and frequently used apps and files. Basically Fusion Drive learns as it goes, so a photo that was just transferred to the machine won't be in the SSD, but if that same photo is opened for a number of times it will be transferred to the SSD tier for faster access.

Thank you! They say in their most used applications, such as Photoshop CC and Lightroom. Sometimes while applying touch up processes the input with the mouse will delay in rendering or even lock up. I have not been able to duplicate the issue but noticed that Spotlight was taking up quite a bit of resources so have disabled it for the time being. The tiered storage is a neat idea because it takes the headaches of deciding what should go where physically but either it's not functioning as intended or just needs a larger SSD to allow CoreStorage to work with more free space on the SSD. I have a DMG of El Capitan, should I try to lobby for a fresh installation on discrete SSD/HDD volumes or try Fusion with a larger SSD?