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vultr live snapshots
Hi,
With Vultr you can take a snapshot of a running vps. What happens if the disk is modified while the snapshot is occurring? (Say a database transaction that occurs in between the start of the snapshot and the end?) Does the snapshot process "freeze" the VPS until the snap is over, to maintain consistency? Any ideas? I could, of course, as them but I thought I would hit up the LET crowd first.
-Adam
Comments
I think the safe assumption is that anything receiving constant writes during the process may be corrupted, but it's probably a good idea to ask their support for clarification. Just imagine an InnoDB database receiving constant changes during a live backup of the data, for example.
I would highly recommend that you do a SQL dump as a second layer of backup protection
I guess just running a DB dump before the snapshot will do the trick. I will ask Vultr and see what they have to say.
you should shutdown the vps before doing the snapshot.
Someone (a non-staff member) on the vultr forums said this :
Is this r1 I wonder or something else. It sounds non trivial for sure
Agreed, sounds very complex to implement correctly.
It's actually a QEMU feature: http://wiki.qemu.org/Documentation/CreateSnapshot
https://kashyapc.fedorapeople.org/virt/lc-2012/snapshots-handout.html (really good read)
The snapshot will be a consistent state of the disk. The reason it is still recommended to shutdown the VPS is because the filesystem may still be in an inconsistent state wrt the parts of the filesystem that have been written to disk.