multi level storage for SSD/HDD hybrid systems with metadata ejection

Chiyoung –

Thanks for a good suggestion.
In the past, we discussed the cache management on the hierarchical storage layer consisting of memory, SSD, and hard disks.
However, we didn’t make much progress at that time because of several reasons (e.g., feature prioritization for releases, market demands on that feature).
I think it is worthwhile to revisit this by considering various factors.

Benjamin ----

Object-stores designed at the outset for large-scale disk storage implement their metadata storages on separate, usually SSD, media. Since we are moving in this direction with DGM and metadata ejection, it would be a good idea (probably essential) to make sure we can direct ejected metadate to SSD even if the values are stored on HDD.