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The following page has been changed by SteveLoughran: http://wiki.apache.org/hadoop/HadoopIsNot The comment on the change is: fix the bullets ------------------------------------------------------------------------------ We see a lot of emails where people hear about Hadoop, and think it will be the silver bullet to solve all their application/datacentre problems. It is not. It solves some specific problems for some companies and organisations, but only after they have understood the technology and where it is appropriate. If you start using Hadoop in the belief it is a drop-in replacement for your database or SAN filesystem, you will be disappointed. - == Hadoop is not a substitute for a database == + == Apache Hadoop is not a substitute for a database == Databases are wonderful. Issue an SQL SELECT call against an indexed/tuned database and the response comes back in milliseconds. Want to change that data? SQL UPDATE and the change is in. Hadoop does not do this. @@ -43, +43 @@ There are some very high-end filesystems out there: GPFS, Lustre, which offer fantastic data availability and performance, usually by requiring high end hardware (SAN and infiniband networking, RAID storage). Hadoop HDFS cheats, delivering high local data access rates by running code near the data, instead of being fast at shipping the data remotely. Instead of using RAID controllers, it uses non-RAIDed storage across multiple machines. - * It is not (currently) Highly Available. The Namenode is a ["SPOF"]. + * It is not (currently) Highly Available. The Namenode is a ["SPOF"]. - * It does not (currently) offer real security. It is probably less secure than Sun's original NFS filesystem. + * It does not (currently) offer real security. It is probably less secure than Sun's original NFS filesystem. Because of these limitations, if you want a secure filesystem that is always available, HDFS is not yet there. You can run Hadoop MapReduce over other filesystems, however.
