Each data has to be written on the host itself and on the two remote ones so you are going to have 1000 mbps / 2 (external replicas ) / 8 (bit/bytes) = a max of 62.5 MB/s sustained throughput shared between all the VMs and this ignoring all the overheads. In practice it will be much less ending in a barely usable environment.

I am currently in this type of setup (replica 2 arbiter 1 on 1 gbit/s both storage and oVirt connectivity) and the maximum write (sequential) speed I can reach is aprox 89 MB/s. I guess with replica 3 the maximum will be as Simone stated. My maximum read speed is aprox 500 MB/s despite that local NVMe is capable of 1.3 GB/s and I guess FUSE is not using the local brick no matter I have set it up with cluster.use-local (or whatever it was called). If possible , get a 10 gbit/s connectivity or multiple gbit interfaces ( as I'm planing to do in the nearest future). Best Regards, Strahil Nikolov