A number of production rings are not fully rebalanced e.g.
matthew@tsk:~/operations/swift-ring$ swift-ring-builder codfw-prod/object-1.builder | grep regions 65536 partitions, 3.000000 replicas, 1 regions, 4 zones, 76 devices, 11.48 balance, 0.00 dispersion matthew@tsk:~/operations/swift-ring$ swift-ring-builder codfw-prod/object-1.builder rebalance Reassigned 1344 (2.05%) partitions. Balance is now 3.82. Dispersion is now 0.00 matthew@tsk:~/operations/swift-ring$ swift-ring-builder codfw-prod/object-1.builder | grep regions 65536 partitions, 3.000000 replicas, 1 regions, 4 zones, 76 devices, 3.82 balance, 0.00 dispersion
Before we deploy any automatic ring management, we want all the rings to be properly balanced. This will involve rebalancing and redeploying the rings. (the rebalance target in swift-ring doesn't seem to quite get this right).