Storage Journey, Part 3: Arrived at DRBD & LINSTOR

After Ceph (Part 1) and Vitastor (Part 2) we have arrived at DRBD and LINSTOR — and stayed.

What DRBD is

DRBD is a shared-nothing, replicated storage solution: It mirrors the content of block devices in real time between hosts. Technically, DRBD sits as a kernel module at the very bottom of the I/O stack — directly above the backing device, transparent to the layers above.

Real-time & synchronous: Write operations are considered complete only when they reside on all connected nodes (synchronous mode) — or locally, with asynchronous replication over distance.
Shared-nothing: no central SAN, no single point of failure.
Quorum & Split-Brain Handling: DRBD comes with its own quorum (typically three replicas or a diskless tiebreaker), which precisely mitigates the classic HA pitfalls.

DRBD: Block-Replikation zwischen Knoten — shared-nothing, kein zentrales SAN

LINSTOR as Orchestration

Manually managing individual DRBD resources doesn't scale. LINSTOR manages the volumes cluster-wide, and the LINSTOR-Proxmox-Plugin integrates the whole directly into Proxmox:

drbd: drbdstorage
    resourcegroup defaultpool
    content images,rootdir
    controller 10.11.12.13

This allows active VMs to be live-migrated in seconds — without downtime and without central SAN. Via resource groups, the replica count is set centrally. Combined with a Proxmox-HA-Cluster this yields a full-fledged, SAN-free HA platform.

Operational Tip

When LVM, DRBD and LINSTOR work together, the global_filter belongs in lvm.conf:

global_filter = [ "r|^/dev/drbd|", "r|^/dev/mapper/[lL]instor|" ]

Otherwise high CPU load or hanging LVM operations loom, because LVM scans the DRBD devices as well.

Why It Stays

DRBD/LINSTOR combines for us the best: low latency on own hardware, true high availability, clean Proxmox integration and a commercial support path via LINBIT. Exactly this mix we sought after the journey through Ceph and Vitastor.

FAQ

Is there commercial support for DRBD and LINSTOR?+

Yes. There is a commercial support path via LINBIT — exactly this mix convinced us after the journey through Ceph and Vitastor: low latency on own hardware, true high availability, clean Proxmox integration, and a contact in an emergency. For productive customer data, the support path was a decisive criterion over younger alternatives.

How does DRBD handle split-brain?+

DRBD comes with its own quorum, typically three replicas or a diskless tiebreaker, which precisely mitigates the classic HA pitfalls. In synchronous mode a write is considered complete only when it resides on all connected nodes. Over distance, asynchronous replication is also possible, where writes are acknowledged locally.

Is there a typical pitfall when operating with LVM?+

Yes. When LVM, DRBD, and LINSTOR work together, a global_filter belongs in lvm.conf that excludes the drbd and Linstor devices from scanning. Otherwise high CPU load or hanging LVM operations loom. Once configured, active VMs can be live-migrated in seconds via the LINSTOR-Proxmox plugin — without downtime and without a central SAN.