Erasure coding is only used for local duplication. If you have cross-site or cross-machine copies, you really don't want the speed of the rebuild to be dominated by available network bandwidth.
For many datahoarding things “when I drive over to my friend’s house and retrieve the drives” is often enough for replicating restore speed.
I guess it depends. I run minio with erasure coding but I also have 2x100gb interconnects between nodes and even with NVMEs I’m not noticing any performance issues with rebuilds. That said with most disks I could see how this could be a problem
I wish I had 100Gbps interconnects! My network is only 10Gbps.
There are three copies of the data as part of ceph's replication. Note this is not replication for backup purposes, erase a file and all objects composing the file are gone. Ceph replication is for comparing checksums and that for guaranteeing integrity.