On a single host, you could do this with LVM. Add a pair of disks, make them a RAID 1, create a physical volume on them, then a volume group, then a logical volume with XFS on top. To expand, you add a pair of disks, RAID 1 them, and add them to the LVM. It's a little stupid, but it would work.
If multiple nodes are not off the table, also look into seaweedfs.
Also consider how (or if) you are going to back up your hoard of data.