[SOLVED] VMs Live Migration - how does it work with Proxmox and VMs on local disks

[gargantua]

Hi for everyone!

Sorry for dummy question but i didn't find answer on it anywhere:
How does Proxmox VMs "Live migration" work if all Proxmox nodes and VMs there have only local disks which placed on HW nodes where VMs placed?
How is it happening without temporary VM's stop?

For example:
On Proxmox node 1 i have one VM with 1TB disk with data.
Software on this VM use this disk all time.

I need to migrate this VM without downtime and run Live Migration.
How Proxmox can keep data consistency during live migration without stopping of writing on VM's disk and temporary bring down VM?

Thanks in advacnce.

 

[bbgeek17]

Hi @gargantua, welcome to the forum.

At a high level: the copy of the 99.9% of the data will be done in the background without interrupting VM operation , while for the last 0.1% the VM/QEMU will enter a pause/suspend type of state when the cutover is done. Most OS/Applications can tolerate this IO pause and continue operating after the resume. However, some will not.

Cheers

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Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[gargantua]

Hi @gargantua, welcome to the forum.

At a high level: the copy of the 99.9% of the data will be done in the background without interrupting VM operation , while for the last 0.1% the VM/QEMU will enter a pause/suspend type of state when the cutover is done. Most OS/Applications can tolerate this IO pause and continue operating after the resume. However, some will not.

Cheers

---

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

Thanks a lot!

As i understood while 99.9% data is copied VM will work from source Proxmox node and once 99.9% data is ready on destination node will be short suspend for copy memory, cpu state and rest data and after that VM will start work from Destination Proxmox node.
am i right?

 

[bbgeek17]

As i understood while 99.9% data is copied VM will work from source Proxmox node and once 99.9% data is ready on destination node will be short suspend for copy memory, cpu state and rest data and after that VM will start work from Destination Proxmox node.
am i right?

Yes, your understanding of the general model is correct.

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Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[gargantua]

Thanks

Yes, your understanding of the general model is correct.

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Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

Thanks a lot. It's really helped with right understanding .

 

[bbgeek17]

Great. You can mark this thread as solved by editing the first message and selecting the appropriate subject prefix. This helps keeping the forum tidy.

Cheers

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Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox