Synology NAS FS2500 Hardware Installation Manual page 13

3 Insert the loaded drive tray into the empty drive bay. Push the handle inward to secure the drive tray.
Note: Make sure that the drive tray is completely inserted. Otherwise, the drive might not function properly.
4 Repeat the steps above to install the other drives you have prepared.
5 Drives are numbered as shown below.
Note: If you plan to create a RAID volume, we recommend installing drives of identical size to make the best
use of drive capacity.
13 Chapter 2: Hardware Setup