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The following page has been changed by CraigMacdonald: http://wiki.apache.org/hadoop/MountableHDFS The comment on the change is: minor formatting changes; link to permissions issues ------------------------------------------------------------------------------ Requirements: + 1. a Linux kernel > 2.6.9 or a kernel module from FUSE - i.e., you compile it yourself and then modprobe it. Better off with the former option if possible. (Note for now if you use the kernel with fuse included, it doesn't allow you to export this through NFS so be warned. See the FUSE email list for more about this.) - 1. a Linux kernel > 2.6.9 or a kernel module from FUSE - i.e., you - compile it yourself and then modprobe it. Better off with the - former option if possible. (Note for now if you use the kernel - with fuse included, it doesn't allow you to export this through NFS - so be warned. See the FUSE email list for more about this.) - 2. FUSE should be installed in /usr/local or FUSE_HOME ant + 2. FUSE should be installed in /usr/local or FUSE_HOME ant environment variable - environment variable To build: - 1. in HADOOP_HOME: ant compile-contrib -Dcompile.c++=1 -Dfusedfs=1 + 1. in HADOOP_HOME: `ant compile-contrib -Dcompile.c++=1 -Dfusedfs=1` - NOTE: for amd64 architecture, libhdfs will not compile unless you edit the Makefile in src/c++/libhdfs/Makefile and set OS_ARCH=amd64 - (probably the same for others too). + (probably the same for others too). See [https://issues.apache.org/jira/browse/HADOOP-3344 HADOOP-3344] === CONFIGURING === + Look at all the paths in fuse_dfs_wrapper.sh and either correct them or set them in your environment before running. (note for automount and mount as root, you probably cannnot control the environment, so best to set them in the wrapper) - Look at all the paths in fuse_dfs_wrapper.sh and either correct them - or set them in your environment before running. (note for automount - and mount as root, you probably cannnot control the environment, so - best to set them in the wrapper) === INSTALLING === - 1. mkdir /mnt/dfs (or wherever you want to mount it) + 1. `mkdir /mnt/dfs` (or wherever you want to mount it) + 2. `fuse_dfs_wrapper.sh dfs://hadoop_server1.foo.com:9000 /mnt/dfs -d` and from another terminal, try `ls /mnt/dfs` - 2. fuse_dfs_wrapper.sh dfs://hadoop_server1.foo.com:9000 /mnt/dfs -d - ; and from another terminal, try ls /mnt/dfs If 2 works, try again dropping the debug mode, i.e., -d + (note - common problems are that you don't have libhdfs.so or libjvm.so or libfuse.so on your LD_LIBRARY_PATH, and your CLASSPATH does not contain hadoop and other required jars.) - (note - common problems are that you don't have libhdfs.so or - libjvm.so or libfuse.so on your LD_LIBRARY_PATH, and your CLASSPATH - does not contain hadoop and other required jars.) === DEPLOYING === in a root shell do the following: - 1. add the following to /etc/fstab - + 1. add the following to /etc/fstab + {{{ - fuse_dfs#dfs://hadoop_server.foo.com:9000 /mnt/dfs fuse + fuse_dfs#dfs://hadoop_server.foo.com:9000 /mnt/dfs fuse -oallow_other,rw,-ousetrash 0 0 - -oallow_other,rw,-ousetrash 0 0 + }}} + 2. Mount using: `mount /mnt/dfs`. Expect problems with not finding fuse_dfs. You will need to probably add this to /sbin and then problems finding the above 3 libraries. Add these using ldconfig. - 2. mount /mnt/dfs Expect problems with not finding fuse_dfs. You will - need to probably add this to /sbin and then problems finding the - above 3 libraries. Add these using ldconfig. Fuse DFS takes the following mount options (i.e., on the command line or the comma separated list of options in /etc/fstab: - + {{{ -oserver=%s (optional place to specify the server but in fstab use the format above) -oport=%d (optional port see comment on server option) -oentry_timeout=%d (how long directory entries are cached by fuse in seconds - see fuse docs) @@ -85, +72 @@ -onotrash (opposite of usetrash) -odebug (do not daemonize - aka -d in fuse speak) -obig_writes (use fuse big_writes option so as to allow better performance of writes on kernels >= 2.6.26) - + }}} The defaults are: - + {{{ entry,attribute_timeouts = 60 seconds rdbuffer = 10 MB protected = null debug = 0 notrash private = 0 - + }}} === EXPORTING === Add the following to /etc/exports: - + {{{ - /mnt/hdfs *.foo.com(no_root_squash,rw,fsid=1,sync) + /mnt/hdfs *.foo.com(no_root_squash,rw,fsid=1,sync) - + }}} NOTE - you cannot export this with a FUSE module built into the kernel - e.g., kernel 2.6.17. For info on this, refer to the FUSE wiki. @@ -112, +99 @@ === RECOMMENDATIONS === - 1. From /bin, ln -s $HADOOP_HOME/contrib/fuse-dfs/fuse_dfs* . + 1. From /bin, `ln -s $HADOOP_HOME/contrib/fuse-dfs/fuse_dfs* .` + 2. Always start with debug on so you can see if you are missing a classpath or something like that. + 3. use -obig_writes - === PERFORMANCE === + === KNOWN ISSUES === + 1. if you alias `ls` to `ls --color=auto` and try listing a directory with lots (over thousands) of files, expect it to be slow and at 10s of thousands, expect it to be very very slow. This is because `--color=auto` causes ls to stat every file in the directory. Since fuse-dfs does not cache attribute entries when doing a readdir, - 1. if you alias ls to ls --color=auto and try listing a directory with lots (over thousands) of files, expect it to be slow and at 10s of thousands, expect it to be - very very slow. This is because --color=auto causes ls to stat every file in the directory. Since fuse-dfs does not cache attribute entries when doing a readdir, - this is very slow. see https://issues.apache.org/jira/browse/HADOOP-3797 + this is very slow. see [https://issues.apache.org/jira/browse/HADOOP-3797 HADOOP-3797] + 2. Writes are approximately 33% slower than the DFSClient. TBD how to optimize this. see: [https://issues.apache.org/jira/browse/HADOOP-3805 HADOOP-3805] - try using -obig_writes if on a >2.6.26 kernel, should perform much better since bigger writes implies less context switching. - 2. Writes are approximately 33% slower than the DFSClient. TBD how to optimize this. see: https://issues.apache.org/jira/browse/HADOOP-3805 - try using -obig_writes - and if on a >2.6.26 kernel, should perform much better since bigger writes implies less context switching. 3. Reads are ~20-30% slower even with the read buffering. - + 4. fuse-dfs and underlying libhdfs have no support for permissions. See [https://issues.apache.org/jira/browse/HADOOP-3536 HADOOP-3536] == Fuse-j-HDFS == - see https://issues.apache.org/jira/browse/HADOOP-4 + see [https://issues.apache.org/jira/browse/HADOOP-4 HADOOP-4] == HDFS-FUSE ==
