CEPH Configuration verification

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ohwrd21

New Member
Nov 20, 2025
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Hi everyone,

I’d like to ask for some guidance regarding the minimum replica settings in Ceph.

Here’s my current setup:

  • I have 3 Proxmox nodes.
  • Two nodes are used as primary hosts for running VMs.
  • The third node is only acting as a quorum (no VM workloads).
My question is:
Is it possible to force the Ceph minimum replica (min_size) to 1 via CLI instead of the default value of 2?

My goal is to ensure that if one of the main nodes fails during HA, the remaining node can still recover and run the VM without interruption.

I understand there may be risks involved, but I’d like to know if this setup is supported or recommended in this kind of environment.

Any insights or best practices would be greatly appreciated.

Thanks in advance!
 
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As others have mentioned, it is technically possible to set size=2 and min_size=1, but it does come with risks.

From a Proxmox and Ceph perspective, this configuration is not recommended. While it may not be explicitly unsupported, the fact that you cannot set min_size=1 from the GUI suggests that it is intentionally discouraged.

In this kind of setup, you would not be able to fully benefit from Ceph’s core strengths, such as data redundancy and self-healing capabilities. During a failure, the cluster effectively operates with a single copy of the data, which significantly reduces reliability.

Given this, it might be more practical to consider alternative approaches. For example, you could accept some RPO and use ZFS replication, or introduce a NAS and use shared storage such as NFS.
 
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