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Hm yeah, in some sense I like the things to be more orthogonal, i.e. container images vs. the file system On the other hand I think storage and networking shou
by chubot 4y ago
Hm yeah, in some sense I like the things to be more orthogonal, i.e. container images vs. the file system
On the other hand I think storage and networking should be more unified, and the differential compression and caching you get from layers is important
I suspect that doing the layers at the logical level (files) , like overlayfs, rather than the physical level (blocks) is also better for containers, but I'd be interested to read any comparisons
- cmurf 4y agoIt depends on the workload. Copy-up is more expensive than snapshots. If it's ext4+overlayfs, then copy-up is really expensive (full file copy), whereas if it's btrfs or XFS then it's reflink copies. Much more efficient. But btrfs snapshots in effect are instant reflink copies. But then overlayfs has the benefit of shared pages. Also, at least Btrfs snapshots are more logical, like files; than physical, like blocks. Whereas LVM snapshots are separate (logical) block devices, Btrfs snapshots are file b-trees on the same file system. Maybe the overlay2 graph driver (the driver used in Docker or Podman to interface with the kernel) is getting more usage and thus maturing more quickly, compared to the btrfs graph driver? I think upstream Docker/Moby are defaulting to the btrfs graph driver if /var/lib/docker is on Btrfs. Meanwhile on Fedora where Btrfs is the default for desktops, and Cloud edition, Podman defaults to overlay2 graph driver no matter the underlying file system.