public String getDataRoot() {
        if (dataRoot == null) {
            dataRoot = mustGetProperty(DATA_ROOT);
        }
        return dataRoot;
    }
The path where realtime segments declare.
<pre>
    .../rt/table/tableA/host0/seg0_0 ... segN_0
    .../rt/table/tableA/host1/seg0_1 ... segN_1
</pre>
indexr-server/src/main/java/io/indexr/server/IndexRConfig.java