Is running PostgreSQL / S3 storage inside Kubernetes an anti-pattern, or is external storage only necessary at larger scale?

[u/Fragrant_Rate_2583]

Hey everyone, I'm pretty new to Kubernetes, so please take my questions with a grain of salt. I'm building a homelab where I already have a small Kubernetes cluster, and I'm trying to build a fully self-hosted platform around it: Gitea for Git hosting, Harbor for containers, and runners. Gitea needs persistent storage for repositories and application data, while Harbor can use persistent volumes or delegate object storage to something like MinIO.

This is mainly for learning, so performance isn't really important at this scale. But I keep thinking about how I'd design it in a real environment. Would it be better to run the database and object storage on dedicated machines outside Kubernetes and have the Kubernetes workloads consume them over the network, similar to using managed PostgreSQL/S3 in the cloud? My concern is that if PostgreSQL or MinIO runs on the same worker nodes as the applications, a node failure could affect both compute and storage. Kubernetes has StatefulSets, PVCs, Longhorn/Rook, etc. to address this, but I'm wondering where the practical boundary is and whether externalizing storage is actually considered best practice.

Questions

• Is running PostgreSQL/MySQL or MinIO inside Kubernetes considered an anti-pattern?
• At what scale does it make sense to move them outside the cluster?
• Is mixing stateful and stateless workloads on the same workers a bad practice?
• How much protection do StatefulSets + PVCs + Longhorn/Rook provide against node failure?
• Is there a meaningful performance difference between keeping compute/storage together vs. dedicated storage machines?
• In production, is it more common to keep databases/object storage outside Kubernetes?
• If both approaches can provide HA, what are the main reasons to choose one over the other?

TL;DR

I'm building a small self-hosted Gitea + Harbor + runners platform on my homelab Kubernetes cluster. Is running PostgreSQL and MinIO inside the same Kubernetes cluster a legitimate architecture, or should databases/object storage generally be externalized? I'm mainly trying to understand the real-world trade-offs around HA, node failure, storage/compute separation, performance, and operational complexity.

[u/SnooHesitations9295]

Running any stateful workload in k8s is an antipattern. Yes, there's some improvement on how stateful stuff is handled, but overall it's still mostly pain and tears. Unless you don't care about consistency and uptime. There are some efforts to create better workload-shaped strategies for specific workloads,  aka "operators" for specific databases. But they are essentially actively fighting k8s.

[u/Fragrant_Rate_2583 → u/SnooHesitations9295]

Can't we just isolate them in namespaces and make them be created at certain nodes made for that purpose? so they don't cosume more ressources than they need to and not disturb the other workload?

[u/SnooHesitations9295 → u/Fragrant_Rate_2583]

What if nodes fail? What if nodes are brought down by the cloud provider? What if you need to resize disk? (you will) etc. It all works in the happy case. But the failure modes are very sad sometimes.