DRBD and LINSTOR are open source building blocks for replicated block storage, developed by LINBIT. DRBD mirrors a block device between cluster nodes in real time, so that a standby node can take over when the primary fails and only changed blocks are resynchronised afterwards. LINSTOR manages many DRBD-replicated volumes across a cluster through a controller and per-node satellites, and offers a Kubernetes CSI driver. It also integrates with platforms such as Proxmox VE and OpenNebula. Operators use the combination for highly available storage under virtualisation and container clusters. You deploy it yourself on your own servers; LINBIT also sells a subscription with certified binaries and support.
LINBIT HA-Solutions GmbH is headquartered in Vienna, Austria, with a US office in Portland, Oregon. DRBD is free software under the GNU GPL version 2 and has been part of the Linux kernel since 2009. As the software runs on hardware you choose, replicated data stays in the EU data centres where you install it, and the code can be inspected.