Sizing Guide

Start with → 2 vCPU · 4 GB RAM · 40 GB SSD

What that box handles

• ≈ 9 bridges instances (e.g. OPC UA ➜ Redpanda) plus one bridge instance that forwards from the local Redpanda to an external MQTT broker

• ≈ 900 tags at 1 message / second each

• Keeps seven days of history under the default cluster retention (log_retention_ms = 7 days)

• Runs comfortably below 70 % CPU and I/O on a Hetzner CAX21 / CX32-class VM or Raspberry Pi 4

Disk usage in practice

Redpanda writes 128 MiB segments; a segment can be deleted only after it is closed. With Snappy compression, a typical 200 B JSON payload shrinks to ≈ 20 B. Allowing a 5 GB safety buffer, a 40 GB SSD gives ≈ 35 GB usable history ≙ ~2.8 billion messages.

Need more? Shorten retention (either during install with internal.redpanda.redpandaServiceConfig.defaultTopicRetentionMs or later on the topic level using rpk) or enlarge the disk.

Memory

Component	Rule of thumb
Redpanda	≈ 2 GB · cores + 1.5 GB head-room (Seastar rule)
Agent + supervision	≈ 150 MB
Each extra pipeline	≈ 100 MB

CPU

One core is kept busy by Redpanda. One additional core comfortably covers the agent and the first dozen pipelines doing light transforms. Heavy parsing, encryption, or synchronous HTTP calls may warrant more cores or a faster CPU.

Easy vertical scaling

UMH Core is stateless besides the /data volume. To grow:

1. Stop the container

2. Move or resize the volume / attach it to a bigger VM

3. Start the same image — no reinstall or re-configuration required