What do you mean by JBOD? Is it recommended in the Hadoop cluster?
JBOD is an alternative to using a RAID configuration. Rather than configuring a storage array to use a RAID level, the disks within the array are either spanned or treated as independent disks. Spanning configurations use a technique called concatenation to combine the capacity of all of the disks into a single, large logical disk. HDFS itself will take care of fault-tolerance and avoid data loss due to data redundancy/backup available in multiple data nodes. Since the NameNode is a single-point-of-failure in HDFS we could make use of RAID in name nodes as it requires a more reliable hardware setup. HDFS clusters do not benefit using RAID for data storage, as the redundancy that RAID provides is not required since HDFS handles it by replicating data on different data nodes. RAID striping used to increase the performance turns out to be slower than the JBOD (Just a bunch of disks) used by HDFS which round-robin across all disks. It’s because, in the RAID, the read/write operations are limited by the slowest disk in the array. In JBOD, the disk operations are independent, so the average speed of operations is greater than the slowest disk. If a disk fails in JBOD, HDFS can continue to operate without it, but in a RAID if a disk fails the whole array becomes unavailable. RAID is recommended for NameNode to protect corruptions against metadata while JBOD is recommended for Datanode.
JBOD == Just a Bunch of Ordinary Disks or Just a Bunch Of Disks.
And the answer is wrong when it comes to the MapR-FS.
MapR does stripe across disks. HDFS does not.
MapR works on Raw disk or even cooked chunks. HDFS does not work on raw disk or cooked chunks but sits on Linux file system.
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