Quantcast File System 1.2 for ARM71

I have been using the Quantcast File System (QFS) as my primary distributed file system on my ODROID XU4 cluster.  Due to QFS’s low memory footprint. it works well with Spark, allowing me to assign as much of the ODROID XU4’s limited 2 GB RAM footprint to the Spark executor running on a node. Recently, QFS 1.2 was released. This version brings many features and updates, many not relevant to my ODROID cluster use case. However, the most notable updates relevant to the ODROID XU4 cluster include: Correct Spark’s ability to create a hive megastore on a new QFS instance (QFS-332) Improved error reporting in the QFS/HDFS shim HDFS shim for the Hadoop 2.7.2 API, which the latest versions of Spark use. In this post, I will update the ODROID XU4 cluster to use QFS 1.2.0. I have also updated my original post on using QFS with Spark, which you should use if you are starting from scratch. Install  QFS 1.2 cd /opt Read More …

Adding a New Node to the ODROID XU4 Cluster

I recently acquired another ODROID XU4 device (and a MicroSD card for bulk storage) to add it to my XU4 cluster. This new node brings my node count to five. Adding a new node to the cluster is relatively straight forward, but there are a lot of details. In the modern datacenter, this operation would be accomplished through a package manager, which would build the new node according to an image. However, I haven’t set up package management on my cluster so I will need to sit up the new node manually. In the original cluster configuration, I used a 5-port ethernet switch for the internal network. Given that there was an open port, no additional hardware beyond the new node is needed. However, if I were to add a sixth node (or beyond), I would need to update my ethernet switch to something such as an 8-port switch. I will also note that using the 40 mm PCB spacers I originally ordered makes Read More …

Connecting to HDFS from an computer external to the cluster

Since I have set up my ODROID XU4 cluster to work with Spark from a Jupyter web notebook, one of the little annoyances I have had is how inefficient it was to transferring data into the HDFS file system on the cluster.  It involved downloading data to my Mac laptop via a web download, transferring that data to the master node, then running hdfs dfs -put  to place the data onto the file system. While I did set up my cluster to create an NFS mount, it can be very slow when transferring large files to HDFS. So, my solution to this was to install HDFS on my Mac laptop, and configure it to use the ODROID XU4 cluster. One of the requirements for an external client (e.g., your Mac laptop) to interact with HDFS on a cluster is that the external client must be able to connect to every node in the cluster. Since the master node of the cluster was Read More …

Using the Quantcast File System with Spark on the ODROID XU4 Cluster

I used to work at a company named Quantcast, which is known for processing petabyte-scale data sets. When operating at that scale, any inefficiency in your data infrastructure gets multiplied many times over. Early on, Quantcast found that the inefficiencies in Hadoop literally cost them by requiring more hardware to obtain certain levels of performance. So Quantcast set out to write a highly efficient big data stack. At the bottom of that stack was Quantcast’s distributed file system called QFS. Quantcast open-sourced QFS, and performed several studies to show the efficiency gains QFS had over HDFS. Given the first hand experience I have had with QFS performance, I thought it would interesting to get it running on the ODROID XU4 cluster in combination with Spark to see how much QFS would improve processing speeds in our set up. Spoiler alert: there was no time improvements, but QFS required less memory than HDFS, allowing me to assign more RAM to Spark. Installing Read More …

Installing Spark onto the ODROID XU4 Cluster

While installing and using Apache Hadoop on the ODROID XU4 cluster is cool, my ultimate goal was to get the more modern Apache Spark application for data analysis. In this post, we will not only install Spark, but also install the Jupyter Notebook for interacting with Spark conveniently from your computer’s browser. The installation instruction here will install Saprk and run it as a stand alone cluster in combination with the HDFS service we have previously installed. Installing Spark ends up being much simpler than installing Hadoop, but I found it to be more temperamental than Hadoop. Most notably, Spark is sensitive to the different CPU core speeds of the heterogenous octal-core CPU that the XU4 uses. If the Spark processes would run on the slower cores of the CPU, the master node would think the slave processes are timing out (missing a heartbeat), in turn restarting the executors on the slave nodes. This causes very inefficient repetition of work Read More …

Running the Word Count Job with Hadoop

Now that we have Hadoop up and running on the ODROID XU4 cluster, let’s take it for a spin. Every technical platform has a “Hello World” type project, and for Hadoop and other map-reduce platforms, it is Word Count. In fact, the Apache Hadoop MapReduce Tutorial uses Word Count to demonstrate how to write a Hadoop job.  We are going to use that tutorial’s code. However, at the time of this writing the WordCount example on the Apache Hadoop site has a bug in it. I’ve corrected that bug and posted the updated code to my Github repository for the ODROID XU4 cluster project. Log into the master node as hduser. We need to update the environment variables so that you can easily build Hadoop jobs. Do this by editing the .bashrc file and add the following at the end: export JAVA_HOME=$(readlink -f /usr/bin/java | sed “s:bin/java::”).. export PATH=$PATH:/usr/local/hadoop/sbin:/usr/local/hadoop/bin:${JAVA_HOME}/bin export HADOOP_CLASSPATH=${JAVA_HOME}/lib/tools.jar Then grab the corrected Word Count job code from the Read More …

Mounting HDFS with NFS

After setting up the Hadoop installation on the ODROID XU4 cluster, we need to find a way to get data in and out of it. The traditional pattern used when a cluster is on it’s own network such as ours is is to have an edge node where the user logs into, transfers the data to that edge node, then put that data in HDFS from the edge node. Speaking from experience, this is annoyingly to much work. For my personal cluster, I want the HDFS file system to integrate with my Mac laptop. The most robust way to accomplish my goal with HDFS is to have it mounted as a NFS drive. The Hadoop distribution we are using has a NFS server built in. This server is run on the master node, effectively acting as a proxy between the HDFS cluster and the external network. The pros to this approach is that I get the usage paradigm that I want. Read More …

Installing Hadoop onto an ODROID XU4 Cluster

Now is the time when we start to see the fruits of our labor in getting the ODROID XU4 low cost cluster built. We will be installing Hadoop and configuring it to serve an NFS mount that can be mounted on your client computer (e.g., your laptop) to be able to interact with the HDFS file system as if it were another hard drive on your computer. This feature will greatly ease the use of our cluster, as it will minimize the need for a user to log into the cluster to use it. An NFS mount is not the only necessary facet of the cluster to enable the client usage vision, but it is an important one. Before we install Hadoop, let’s discuss what we are trying to accomplish by installing it. Hadoop has three components: the Hadoop File System (HDFS), Yarn, and Map-Reduce. For our purposes, we are most interested in HDFS, but we will play around with the Read More …

Adding the MicroSD Data Drives to the ODROID XU4 Cluster

We are nearly done with the basic set up of the ODROID XU4 four node cluster. The final step is to configure the MicroSD cards that were in the bill of materials as data drives for each node. Before we start, ensure that the cluster is completely powered down and remove the power cords from each node. We will be removing and adding components to the ODROID XU4’s, and it is just best practice to have no power to the device when removing or adding components. The first step is to format each MicroSD card with the ext4 filesystem. Each platform has it’s own instructions for how to do this. I will provide the Mac OS X instructions since that is what I use. In the terminal, do the following: If you don’t have it already, install the Homebrew package management app for OS X. Visit the brew.sh website for instructions. Install the e2fsprogs utility using brew install e2fsprogs With the MicroSD card attached to your computer, Read More …

Configuring DHCP and NAT in ODROID XU4 Cluster

As was discussed in the network design post, we will set up the master node as a router to manage network traffic in and out of the cluster.  Before starting, ensure that all of the slave nodes have been powered down, that your home network is still connected directly to the open port on the cluster’s ethernet switch, that you have collected each node’s MAC address, and that the master node is powered up and you are logged into it via SSH. The first step is to explicitly set up the networking interfaces for both the eth0 and eth1 device on the master node. Note that by default the Ubuntu system that was installed on the master node treats eth0 a as requesting a DHCP lease on the network it is attached to. This is why it got an IP address when it was first powered up. However, we are going to change this. The eth0 interface will be connected Read More …