[staticassertion]

> Depending on how I/O is handled, container I/O can be very slow, whereas a dedicated disk snapshot without CoW/overlays would be much faster.

Do you mean VM I/O can be very slow? I don't think containers should have any overhead, please correct me if I'm wrong though.

[0xbadcafebee]

Container file I/O is very slow. It unpacks the OCI image layers onto the regular host filesystem, then adds overlay filesystems, does copy-on-write, and references files between each layer. For example, doing 10 containerized nodejs app builds simultaneously will swamp the host with iowait. A common hack to is to put the OCI file tree / overlays on a dedicated disk with much higher iops than the boot disk.

[rascul]

> It unpacks the OCI image layers onto the regular host filesystem, then adds overlay filesystems, does copy-on-write, and references files between each layer.

That's just Docker though, right? Does LXC or systemd-nspawn do that?

[staticassertion]

Thank you, I'll have to look into this. I was thinking from a file namespacing perspective there shouldn't be overhead, but it makes sense that adding the overlay filesystems and mounts would impact performance.