How to Replicate a vm between two nodes?

barrynza

New Member
Dec 5, 2020
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Hi There,

I'm trying to achieve a replication of a VM(id100) from Node A to Node B (and vice versa) - so when i make changes on VM that resides on NodeA it replicates that change to NodeB VM, yes i know that must be ZFS but i cant understand when in my scenario i have two nodes both nodes have a 500GB ssd where i want my VM100 to be replicated simple, but not looking simple when i receive the error saying: missing replicate feature on volume 'local-lvm:vm-100-disk-1' (500).
- So i deleted LVM on both nodes both ssds and created ZFS on each as single disk then tried to use replicate feature nope still same error.
Proxmox shouldnt make ZFS mandatory, it should be able to replicate if machines are in Cluster? Any ideas would be appreciated folks?
 
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Stefan_R

Proxmox Staff Member
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Jun 4, 2019
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"Replication" in PVE does *not* mean the VM is configured on multiple nodes. It simply means that the storage will be synced across the network every couple of minutes, so if one node dies, the other can take over the VM via the HA stack. For this to work, *all* disks of a VM must be on a ZFS storage, as we use ZFS recv/send to incrementally sync the disk.

Please refer to our documentation for more.
 

barrynza

New Member
Dec 5, 2020
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"Replication" in PVE does *not* mean the VM is configured on multiple nodes. It simply means that the storage will be synced across the network every couple of minutes, so if one node dies, the other can take over the VM via the HA stack. For this to work, *all* disks of a VM must be on a ZFS storage, as we use ZFS recv/send to incrementally sync the disk.

Please refer to our documentation for more.
Thanks but that is costly, do we have any other option where i can achieve the above?
 

Stefan_R

Proxmox Staff Member
Staff member
Jun 4, 2019
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It is not possible to have a VM on two nodes at once. You can use shared storage, for example ceph, to allow fast failover via our HA stack though.

Please refer to the documentation I've linked above.
 

barrynza

New Member
Dec 5, 2020
14
1
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40
It is not possible to have a VM on two nodes at once. You can use shared storage, for example ceph, to allow fast failover via our HA stack though.

Please refer to the documentation I've linked above.
Thanks Stefan, that is understandable, HA failover is the best way to use in my situation, ceph also requires more drives to achieve the ceph efficiency. Best way is to have the vm disk on shared and use HA failover feature.
 

WOJCIECH

Member
May 14, 2018
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"Replication" in PVE does *not* mean the VM is configured on multiple nodes. It simply means that the storage will be synced across the network every couple of minutes, so if one node dies, the other can take over the VM via the HA stack. For this to work, *all* disks of a VM must be on a ZFS storage, as we use ZFS recv/send to incrementally sync the disk.

Please refer to our documentation for more.

1. What about VM with SQL server working inside. Normally if we want take a coherent snapshot of VM like this, we have to use qm --vmstate 1 for dump memory of VM (beacause of opened buffers by SQL engine and qm agent inside VM).
How works replication by corosync between two nodes VMs - Only snapshots of virtual disks are sending between nodes ?

2. How we can start replicated VMs from second node if main node failed and die ? Is any procedure? Because VMs are not visible, and VM can't start on second node (node for backup)
 
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