Pseudo HA using VM Replication in Proxmox

tuathan

Member
May 23, 2020
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I'm exploring methods to provide redundancy/failover for VMs running on a PVE cluster. I am wondering if, using the Proxmox Replication functionality I can:

1. replicate a VM on Node1 to another node (say Node2) in the cluster at a certain time point T,
2. automatically or manually start the replicated VM (from time point T) on node 2 if node 1 becomes unresponsive/goes down
3. continue running a job on the VM (now on node2) that was running when the VM was replicated at time point

To elaborate on 3., say I have a simple bash script running on the VM on node1 that simply echos an interger to the terminal: 1, 2, 3, 4, 5....
I replicate that VM to node 2 at time point T.
Node 1 goes down at time point T+3 when the interger echoed is "8"
The VM starts on node2 and the bash script echos to the terminal: 6, 7, 8, 9, ......etc i.e. effectively rolling back in time (to time point T) but thats ok.
 
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My other idea is to run the same "Bash script" on two different VMs on two different nodes. THis could also provide redundancy.
 
Hi, did you get any further with this? My thought would be to use a Raspi on a 3rd box to check which one of my proxmox is live. I also thought to have it as a 3rd for a quorum in HA.

Is replication able to be used instead of shared storag for a HA Cluster?

cheers
 
Not exactly.

I have configured a 5 node PVE cluster with VMs accessible via NAT. I created ZFS storage on each PVE node (using some of the hdisks) for VM disks. I then set up VM replication from node 1 to 2, 2 to 3 ... 5 to 1 every 10 mins and using HA could get VMs to migrate and (re-)start automatically (with state up to 10 mins ago) if original node went down but obviously this is not 'live' migration. This only preserves the VM disk state from 0 to 10 mins ago.

See: https://forum.proxmox.com/threads/storage-types-for-ha-and-live-migration.71864/#post-322045

I will probably see what I can do with Proxmox/HA and GlusterFS in terms of preserving CPU/memory state next.
 
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