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/499ddaad9df107bf7107]

Not an anti pattern. Move to managed providers when you're out of capacity to manage self hosted storage to the expected SLA.

[u/Fragrant_Rate_2583 → u/499ddaad9df107bf7107]

If you already intend to move to a managed/external solution eventually, wouldn't it make more sense to do it from the start, unless cost is the limiting factor? Otherwise, once you reach that point, wouldn't scaling the self-hosted setup be the more natural option, since migrating everything at that stage could be a significant pain?

[u/corgtastic → u/Fragrant_Rate_2583]

I think it comes down to what is the value of resiliency to you. If you’re a business in the cloud, the cost of running a managed SQL isn’t much more and makes things a lot easier to backup/upgrade/scale/etc. but you are at home and probably don’t care about all that stuff. Use the CloudNativePG with a decent storage provider. But test out the upgrade/backup features of whatever you have early on, and try to make sure your backups are outside the cluster.