private boolean shouldSnapshotOrFlush() {
      return effectiveInfoRatio < config.getWalMinEffectiveInfoRatio()
          || WALManager.getInstance().shouldThrottle();
    }
Return true iff effective information ratio is too small or disk usage is too large.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/node/WALNode.java