regarding _HDFS_ there is no need to use RAID at all. In addition to @Aayush Kasliwal 's answer, I'd highly recommend to configure Namenode-HA to avoid any single-point-of-failure for HDFS. This also ensures that the Namenode Metadata will be written in multiple copies throughout the JournalNodes (e.g. you can configure multiple directories and you should use e.g. 3 JournalNodes).
Where I see RAID as benefitial are the partitions for OS, logs, ... but of course, this is "below" HDFS