I just finished setting up bidirectional synchronization with an OwnCloud server and an OpenCloud server (both via WebDAV, but OwnCloud using its specific option). The OwnCloud version works great. Additional syncs after the initial one are really fast. But the OpenCloud sync is very slow. It's 60 seconds for a sync that should be a no-op.
I'm actually not 100% sure if this is only related to OpenCloud. The amount of data I'm trying to sync there is also much more than with OwnCloud (about 7GB for OpenCloud). Maybe that is the only reason? But with OpenCloud, I also get the warning:
WARNING: Modtime compare was requested but at least one remote does not support it. It is recommended to use --checksum or --size-only instead
So, I'm assuming this lacking modtime support is the reason why it takes so long? Could specific support for OpenCloud make bisync faster?