Understand simple mechanics first, decide how to act later.
Without –PR there’s no difference from which host to run repair, it runs for the whole 100% range, from start to end, the whole cluster, all nodes, at once.
With –PR it runs only for a primary range of a node you are running a repair.
Let say you have simple ring of 3 nodes with RF=2 and ranges (per node) N1=C-A, N2=A-B, N3=B-C (node tokens are N1=A, N2=B, N3=C). No rack, no DC aware.
So running repair with –PR on node N2 will only repair a range A-B, for which node N2 is a primary and N3 is a backup. N2 and N3 will synchronize A-B range one with other. For other ranges you need to run on other nodes.
Without –PR running on any node will repair all ranges, A-B, B-C, C-A. A node you run a repair without –PR is just a repair coordinator, so no difference, which one will be next time.
Best regards / Pagarbiai
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