Testing HA with 5.3

Discussion in 'Proxmox VE: Installation and configuration' started by txsastre, Dec 8, 2018.

  1. txsastre

    txsastre New Member

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    I have 3 hosts,if one is stopped in 2-3 minutes I can see the VM that host was holding, starts on another host. but when there is only 1 host remaining it does not wake up the VMs that were on.

    I realised that "pvecm expected 1" makes the VMs start.
    *cluster information says that every node has "votes=1
    does this votes 1 related to pvecm expected 1 ?

    Could it be configured the cluster to work in case that there is only 1 host ?
     
  2. spirit

    spirit Well-Known Member
    Proxmox VE Subscriber

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    HA can only work in you have quorum. It's not possible to get it work if you loose more than half total nodes number.

    If you have only 1node up, (and you are sure that the others are done), you can setup "pvecm expected 1", to said "I need only 1 vote to have quorum), to get /etc/pve writeable again, and be able de restart vm on it.

    (but don't forget to set pvecm expected to previous value, we others nodes are back)
     
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  3. txsastre

    txsastre New Member

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    hi thanks for the reply, sorry for the delay, pretty busy here :(

    question, if I have 5 hosts, and 3 go down, the HA will not work with the 2 remaining hosts ?

    yes I tried"pvecm expected 1" and it works, but I have to read more to understand how does proxmox works in this situations, I'm used to xenserver and it can work with only 1 host, also tested oVirt and it also works without touching anything.

    Thanks
     
  4. gosha

    gosha Member

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    Hi!
    HA need quorum. Quorum - more then half nodes.
    For 5 nodes - more then half nodes (quorum) is the more then 5/2=2.5 i.e. 3 nodes.

    Best regards,
    Gosha
     
    #4 gosha, Dec 14, 2018 at 05:27
    Last edited: Dec 14, 2018 at 05:34
  5. txsastre

    txsastre New Member

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    ok. thank you.

    for example, if I have this 3 nodes down, I can use "pvecm expected 1" on the 2 remaining to wake up all the VM and CT ?

    I studying as much as I can proxmox because i want to migrate from xenserver to another hypervisor and I'm trying to find the best option that fits to us.

    our scenario is :
    a primary CPD with 3 nodes and 40-50 VM stored on a SAN iSCSI
    and a secondary (backup) CPD with the same configuration.

    thanks again !
     
  6. Andrew Hart

    Andrew Hart Member

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    Hi,
    What would happen to cause 3 out of five nodes to die? I think if you had a five node cluster, the most you would expect is 1 failure at a time. There is also the point that if you did get it working how you want, then all 40-50 VMs could end up running on one node.
    Your idea of having two physically separated 3 node clusters is a good one BUT if one is just a secondary backup and a single node can run all the 40-50 VMs.....why not have 5 nodes in the primary and 1 in the backup?

    Even better would be to have a nine node cluster spread over three datacentres, but who has three?
    Andrew
     
  7. gosha

    gosha Member

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    I join this approach. And I use a similar configuration in my work.
    I have 4 nodes (the 5th node will be soon) in the main cluster (storage CEPH).
    And a single node with Proxmox VE as a backup server (for VMs and CTs from main cluster). Storage - 4 HDD ZFS RAIDZ-1.

    Gosha
     
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