When some replicas which the relative collection's replicaFactor is 1, it will lost data after executing the REPLACENODE cmd.
It may be the new replica on the target node does not complete revovering, but the old replica on the source node was already be deleted.
At last the target revocery failed for the following exception:
2017-05-18 17:08:48,587 | ERROR | recoveryExecutor-3-thread-2-processing-n:192.168.229.137:21103_solr x:replace-hdfs-coll1_shard1_replica2 s:shard1 c:replace-hdfs-coll1 r:core_node3 | Error while trying to recover. core=replace-hdfs-coll1_shard1_replica2:java.lang.NullPointerException