Forgot to add, this JIRA details the latest security features that are being worked on in Hadoop trunk: https://issues.apache.org/jira/browse/HADOOP-4487. This document describes the current status and limitations of the permissions mechanism: http://hadoop.apache.org/core/docs/current/hdfs_permissions_guide.html.
On Sun, Feb 15, 2009 at 2:35 PM, Matei Zaharia <ma...@cloudera.com> wrote: > I think it's safe to assume that Hadoop works like MapReduce/GFS at the > level described in those papers. In particular, in HDFS, there is a master > node containing metadata and a number of slave nodes (datanodes) containing > blocks, as in GFS. Clients start by talking to the master to list > directories, etc. When they want to read a region of some file, they tell > the master the filename and offset, and they receive a list of block > locations (datanodes). They then contact the individual datanodes to read > the blocks. When clients write a file, they first obtain a new block ID and > list of nodes to write it to from the master, then contact the datanodes to > write it (actually, the datanodes pipeline the write as in GFS) and report > when the write is complete. HDFS actually has some security mechanisms built > in, authenticating users based on their Unix ID and providing Unix-like file > permissions. I don't know much about how these are implemented, but they > would be a good place to start looking. > > On Sun, Feb 15, 2009 at 1:36 PM, Amandeep Khurana <ama...@gmail.com>wrote: > >> Thanks Matie >> >> I had gone through the architecture document online. I am currently >> working >> on a project towards Security in Hadoop. I do know how the data moves >> around >> in the GFS but wasnt sure how much of that does HDFS follow and how >> different it is from GFS. Can you throw some light on that? >> >> Security would also involve the Map Reduce jobs following the same >> protocols. Thats why the question about how does the Hadoop framework >> integrate with the HDFS, and how different is it from Map Reduce and GFS. >> The GFS and Map Reduce papers give a good information on how those systems >> are designed but there is nothing that concrete for Hadoop that I have >> been >> able to find. >> >> Amandeep >> >> >> Amandeep Khurana >> Computer Science Graduate Student >> University of California, Santa Cruz >> >> >> On Sun, Feb 15, 2009 at 12:07 PM, Matei Zaharia <ma...@cloudera.com> >> wrote: >> >> > Hi Amandeep, >> > Hadoop is definitely inspired by MapReduce/GFS and aims to provide those >> > capabilities as an open-source project. HDFS is similar to GFS (large >> > blocks, replication, etc); some notable things missing are read-write >> > support in the middle of a file (unlikely to be provided because few >> Hadoop >> > applications require it) and multiple appenders (the record append >> > operation). You can read about HDFS architecture at >> > http://hadoop.apache.org/core/docs/current/hdfs_design.html. The >> MapReduce >> > part of Hadoop interacts with HDFS in the same way that Google's >> MapReduce >> > interacts with GFS (shipping computation to the data), although Hadoop >> > MapReduce also supports running over other distributed filesystems. >> > >> > Matei >> > >> > On Sun, Feb 15, 2009 at 11:57 AM, Amandeep Khurana <ama...@gmail.com> >> > wrote: >> > >> > > Hi >> > > >> > > Is the HDFS architecture completely based on the Google Filesystem? If >> it >> > > isnt, what are the differences between the two? >> > > >> > > Secondly, is the coupling between Hadoop and HDFS same as how it is >> > between >> > > the Google's version of Map Reduce and GFS? >> > > >> > > Amandeep >> > > >> > > >> > > Amandeep Khurana >> > > Computer Science Graduate Student >> > > University of California, Santa Cruz >> > > >> > >> > >
