Tiering on Smaller Drobos The mSATA SSD is used to accelerate smaller and random reads from the Drobo, while the HDDs are used for storing and streaming larger data such as photos, video, and user documents.
I don’t see anything talking about writes to the Drobo with MSATA, only the reads from the Drobo. I also am unsure what they consider smaller reads, though I would think anything over 50meg would be a larger read.
I don’t have the MSATA so I don’t have any experience with them. Based on what I read about the life expectancy of MSATA in a Drobo I opted out of them, that and the fact the Drobo 5N is plenty fast enough for media streaming to multiple devices without it, I just don’t suggest trying it with “green” drives.