Start Ceph with Single Node to later create Cluster with 3 nodes

[fischedouglas]

I'm not very used to Proxmox...
But meeting the demands of my customers stating to undestanding it a bit.

And I'm facing a problem that is almost like a chiken or egg matter.



I will mention a hypothetical scenario here, but this is one that is very close to what I'm frequently seen on day-to-day...


- 3 Servers with vSphere ESXi, in vCenter, in shared storage, in replicated Vms.

- Lets say that are servers with 2 SSDs and 2 SAS HDDs.
- The total load of the VMs uses 50-60% of the total capacity, so it fits on only two of the available nodes.
- I take one of those servers, migrate(manualy) vms to other two nodes, put Proxmox on it on a dedicated disk.

Here starts the problem!

- I'm not being able to begin a ceph cluster with this only one server.
- So I'm needing to do some acrobatics using LVM on two of those disks, cherrypicking the vms that will fit on that LVM and also fit on the available performance of IOPS and CPU+RAM.

- Do similar things to the second server, and third server.
- Create a Proxmox cluster with those 3.
- Create a Ceph cluster with half of the disks.
- Move from LVM to Ceph.

My Desire/Dream?
Lear how to start a ceph cluster on a single node proxmox where it can begin with 2 pairs of disks.

Convert part of VMs to that node.

And then the a proxmox cluster with two nodes, add the second proxmox node to the ceph cluster.
And after that, the third node.

Any suggestions on how to do that?

 

[RocketSam]

This answer is really belated, but can be useful to those that got here through the search engine.
You can start with a single node ceph cluster.
Don't forget to change settings back to normal after you add more nodes to the pool.

$ ceph config set global mon_allow_pool_size_one true
$ ceph osd pool set <poolname> min_size 1
$ ceph osd pool set <poolname> size 1 --yes-i-really-mean-it
$ ceph config set global mon_warn_on_pool_no_redundancy false
$ ceph health mute POOL_NO_REDUNDANCY