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GCP’s ‘live migrations’ have been doing this for close to a decade or more. Must not be that big of a problem.

by sunshinekitty 1y ago

londons_explore 1y ago
It isn't a problem if you guarantee only one child of the clone lives on - which GCP does.
- matt-p 1y ago
  How do we know that isn't enforced here too?
  - jsnell 1y ago
    Because their main selling point is to run the copies concurrently with the original.
oceanplexian 1y ago
Live Migration on VMWare has been a thing before Google even had a cloud service.
- tanelpoder 1y ago
  VMware even has a vSphere Fault Tolerance product that creates a "live shadow instance" of a VM that mirrors the primary virtual machine (with up to 4 vCPUs). So you can do a quick failover in case of an "immediate planned" failover case, but apparently even when the primary DB goes down. I guess this might work when some external system (like a storage array) goes down in the primary, you can just switch to the other VM (with latest memory/CPU state) and replay that I/O there and keep going... But if there's a hard crash of the primary, if it actually does work, then they must be doing lots of reasoning about internal state change ordering & external device side-effect (somewhat like Antithesis, but for a different purpose). Back in the day, they supported only uniprocessor VMs (with something called vLockstep) and later up to 4 vCPUs with something called Fast Checkpointing. I've always wanted to test this out for fun, by now 15 years have gone by and I've never got to it... https://www.vmware.com/products/cloud-infrastructure/vsphere/fault-tolerance https://www.vmware.com/products/cloud-infrastructure/vsphere...
  - umachin 1y ago
    VMware has also had a patent on live VM cloning (called it VMfork) for quite a few years now. I worked on the team that built related features. Feature itself was in the desktop product. https://blogs.vmware.com/euc/2016/02/horizon-7-view-instant-clone-technology-linked-clone-just-in-time-desktop.html https://blogs.vmware.com/euc/2016/02/horizon-7-view-instant-... Live migration had some very cool demos. They would have an intensive workload such as a game playing and cause a crash and the VM would resume with 0 buffering.

GCP’s ‘live migrations’ have been doing this for close to a decade or more. Must not be that big of a problem.

londons_explore 1y ago

It isn't a problem if you guarantee only one child of the clone lives on - which GCP does.

matt-p 1y ago
How do we know that isn't enforced here too?
- jsnell 1y ago
  Because their main selling point is to run the copies concurrently with the original.

oceanplexian 1y ago

Live Migration on VMWare has been a thing before Google even had a cloud service.

tanelpoder 1y ago
VMware even has a vSphere Fault Tolerance product that creates a "live shadow instance" of a VM that mirrors the primary virtual machine (with up to 4 vCPUs). So you can do a quick failover in case of an "immediate planned" failover case, but apparently even when the primary DB goes down. I guess this might work when some external system (like a storage array) goes down in the primary, you can just switch to the other VM (with latest memory/CPU state) and replay that I/O there and keep going... But if there's a hard crash of the primary, if it actually does work, then they must be doing lots of reasoning about internal state change ordering & external device side-effect (somewhat like Antithesis, but for a different purpose). Back in the day, they supported only uniprocessor VMs (with something called vLockstep) and later up to 4 vCPUs with something called Fast Checkpointing. I've always wanted to test this out for fun, by now 15 years have gone by and I've never got to it... https://www.vmware.com/products/cloud-infrastructure/vsphere/fault-tolerance https://www.vmware.com/products/cloud-infrastructure/vsphere...
- umachin 1y ago
  VMware has also had a patent on live VM cloning (called it VMfork) for quite a few years now. I worked on the team that built related features. Feature itself was in the desktop product. https://blogs.vmware.com/euc/2016/02/horizon-7-view-instant-clone-technology-linked-clone-just-in-time-desktop.html https://blogs.vmware.com/euc/2016/02/horizon-7-view-instant-... Live migration had some very cool demos. They would have an intensive workload such as a game playing and cause a crash and the VM would resume with 0 buffering.