SSD Cache Volume (M.2 and 2.5")
The DS923+ with DSM 7.2 allows SSDs (2.5" and M.2) to be created as a volume, which is ideal for use for PhotoStructure’s /ps/tmp
per PhotoStructure for Docker: Docker volume setup
However 7.2 is still in beta and older Synology products like the DS920+ only support using SSDs as a Synology-managed read/write cache. I have not personally tried it yet, but these scripts (and associated Synology subreddit threads) appear to make it easy to unofficially implement. GitHub - 007revad/Synology_HDD_db: Add your HDD, SSD and NVMe drives to your Synology's compatible drive database