Ceph 2 OSD. 2 Nodes.

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BinaryCrash

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Sep 22, 2019
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Hello,

I have 2 nodes with 1 nvme each.
I was going to set up a lvm-thin for my VMs, but i would like to know if it is possible to create a 2 OSD Ceph pool and the performance impact. If it is good to have it and use HA.

2 nodes, 1 nvme each for osd, 10G SFP+ ports on both.
Would it be a pool with Size = 2 and min size = 1 ?
For a 1TB nvme, PG 128 or 256? (It will not grow in osd number, but could have an upgrade later for bigger capacity)

I am not familiar with ZFS, but i have other nodes in the cluster using ceph (3 osd, pool size 2/1).
I can only use 2 nodes in this case/crush map.

Regards.
 
It is not recommended to have Ceph run on two nodes, especially not when you want to have VM images running on the OSDs. How should Ceph decide which OSD is correct if the two replicas differ? It is no good, don't run Ceph with two OSD only.
 
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ph0x said:
It is not recommended to have Ceph run on two nodes, especially not when you want to have VM images running on the OSDs. How should Ceph decide which OSD is correct if the two replicas differ? It is no good, don't run Ceph with two OSD only.
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Do you recommend any other way to do it?
The objetive is to have like a mirroring on 2 nodes.
To be able to use HA.


EDIT: Forgot to mention i have 2 OSD for this crush map, but i have 5 monitors on other nodes. So will this solve the problem?
 
Last edited:
The recommended way is to have at least three nodes.
If you absolutely can't you should rather use storage replication with zfs than ceph.
 
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I saw something on another topic about using 2 OSD and 3 monitors, and setting noout on the OSD.
I will read about the zfs and storage replication.
Thank you for your help.
 
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