Let's say I have a 5 node cluster, with 3 SSD RAID 10 nodes and a 2 SSD RAID 1 nodes.
Will the RAID 1 nodes slow down the entire network?
How do the Galera cluster writes work? Does it have to wait until the slowest node (RAID 1) finish writing the query or can I write to the RAID 10 nodes and not be affected?
The performance of the cluster is determined by the slowest node.
Each transaction has to be certified by all nodes so if one node is slow it will also drag the rest of the nodes, hence cluster performance will also be affected.
However, in your case since all nodes use SSD and the only difference is the RAID setup then I don't foresee any problems. Just make sure that the network is stable and latency is kept in check.
