What are disadvantages of the Hadoop distribution MapR compared to Cloudera and Hortonworks?
Cloudera and Hortonworks use HDFS, one of the basic concepts of Apache Hadoop. MapR uses its own concept / implementation. Instead of HDFS, you use the native file system directly. You can find a lot of advantages using this approach on the website of MapR.
I wonder what are the disadvantages of this approach?
Answer
I would define MapR a bit differently. It does not use HDFS, but instead of it provides their own distributed file system with NFS interface. which, as well as HDFS is based on local FS.
Main differances are coming from the fact that HDFS is not Posix and other design choices.
1. HDFS is not mutable while MapR is. It can be viewed as advantage, especially if you need it.
2. HDFS is not mountable while MapR is. You can use any existing tools working with Linux FS.
Unrelated to posix:
MapR have small block size and not single point of failure (NameNode).
MapR Has multisite replication.
lets look on dark side also:
a) Having mutable data (instead of not mutable HDFS) makes system more complicated.
b) It is not known (at least for me) to work on huge clusters. (I heard about hundred of nodes).
c) From architecture point (having small blocks) I am not sure how good data locality can be achieved.