I was thinking about creating a storage farm.
I have absolutely no idea if there are any limitations of storing multiple TBs of data.
Are there any physical limitations regarding amount and speed of the storage?
The size limitation for drives is a SATA-Issue...the Raspberry has no SATA routines in it's BIOS.
Usually you have only USB-Ports to connect peripherals, so there are no limits by the USB-controller interface on the size of data-storage. BUT..., these slow USB-2 Ports have shared access with the Ethernet-Adapter. This means you will be slow as hell with many disks connected to them.
You may use an additional controller board for your project solution. Look for "raspberry pidrive" and get an X8XX Controller board to attach.