Natively, you can install 4 SATA HDDs and supplimentary, with a mini PCI-E half size or an addapter, you can have in total 5HDDs/SSDs in your Q1900-ITX box.
I also bought a 2x SATA Syba PCI-Express-Card (2 SATA-Ports with6 Gbit/s, PCI Express 2.0, PCIe x1) and i can squeeze more HDDs.
SATA2 is also working and is recommended if you have HDDs connected to the PCI-E SATAaddon card
Nice! Thanks for your quick reply. So with a mini-pcie half size SSD the motherboard works fine? (because some motherboard doesn't work HDD/SSD in the mini-pcie, becuase it is only for wifi/BT modules).
Thanks again and regards.