Tag Archives: big data

AWS configuration and topology template for Cloudera Hadoop

Planning and Communicating Your Cluster Design

When creating a new Amazon Web Services (AWS) hadoop cluster it is overwhelming for most people to put together a configuration plan or topology.

I’ve done this many times and as part of my focus on tools and templates thought I’d add a template you can use as a basic guideline for planning your Cloudera big data cluster.  The template includes configurations for:

  • instance basics
  • instance list
  • storage
  • operating system
  • CDH version
  • the cluster topology
  • metastore detail for hive, YARN, hue, impala, sqoop, oozie, and Cloudera Manager
  • high-availability
  • resource management
  • and additional detail for custom service descriptors (CSD) for Storm and Redis

No Warranty Expressed or Implied

It’s not meant to be exhaustive as there are many items not covered (AWS security groups, network optimization, dockerization, continuous integration, monitors, etc.) but it is an example of a real-world cluster in AWS (details of instance and AZ changed for security).

Screenshot of the roles and services in the big data design template
Example list of EC2 instances for the cluster plan

Cloudera hadoop cluster configuration template for Amazon Web Services (AWS)

AWS_topology_template

Please feel free to let me know how it works for you and if you have any improvements for it.

Double your effective IO on AWS EBS-backed volumes

Fresh Elastic Block Storage volumes have first-write overhead

At my employer I architect Big Data hybrid cloud platforms for global audience that have to be FAST.  In our cluster provisioning I find we frequently overlook doing an initial write across our volumes to reduce write time during production compute workloads (called pre-warming the EBS volumes).  Per Amazon (http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-prewarm.html) failure to pre-warm EBS volumes incurs a 5-50% loss in effective IOPS.  Worst case that means you could DOUBLE the IO portion of your HDFS writes until each sector has been touched by the kernel.  Amazon asserts that this performance loss, amortized over the life of a disk, is inconsequential to most applications.  For one of our current clusters we have a portion with 8-1TB drives in each of 10 compute nodes as a baseline.  Our estimated pre-warm time is 30 hours on each mount point so if done sequentially that’s 2,400 hours to touch each drive block.

What does this imply?  Without pre-warming we would have added as much as 2,400 additional hours of write latency during initial HDFS writes and that latency could appear in many different places in the stack (HDFS direct writes, Hive postgresql/mysql metadata writes and management, log writes, etc.)

Steps to optimize your EBS writes

Read the AWS document above carefully as it will ERASE EVERYTHING ON THE DISK if you use the first method in their article.  The steps below will execute this safely on disks with existing content.

To pre-warm the drives on your cluster:

  1. stop the cluster services
  2. ssh into each server
  3. execute lsblk and note the mount points (they likely start from /dev/xvdf and go down from there increasing the letter at the end, such as /dev/xvdg, /dev/xvdh, etc.)
  4. unmount each one at a time with sudo umount /ONEMOUNTPOINT
  5. Continue until all mount points are unmounted, meaning there’s nothing shown after the ‘disk’ column as below:
  6. CAUTION:  DO NOT DO THE FOLLOWING ON A MOUNTED DISK AND MAKE SURE YOU USE THE SAME MOUNT FOR BOTH if AND of
  7. execute the following, changing the if= and of= to the same mount pointsudo dd if=/YOURMOUNTPOINT of=/YOURSAMEMOUNTPOINT conv=notrunc bs=1MExample:  sudo dd if=/dev/xvdf of=/dev/xvdf conv=notrunc bs=1M
  8. Wait.  It’ll be a few minutes for a 32GB drive as shown in the Amazon write-up above or 1 day+ for a 1TB drive.
  9. After ALL the processes on the server complete, reboot the server

 

If you’d like to check the process or if your ssh session has expired and you want to ensure you’re still warming execute ps aux|grep YOURMOUNTPOINT , example:  ps aux |grep /dev/xvdf

A far better approach, of course, would be to automate this as part of your cluster deployment process using Chef or equivalent infrastructure automation tool.

Ref: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-initialize.html

Example Big Data dev cluster topology

Below is an example dev cluster topology for a Big Data development cluster as I’ve actually used for some customers.  It’s composed of 6 Amazon Web Service (AWS) servers, each with a particular purpose.  We have been able to perform full lambda using this topology along with Teiid (for data abstraction) on terabytes of data.  It’s not sufficient for a production cluster but is a good starting point for a development group.  The total cost of this cluster as configured (less storage) is under $6/hour.

Here’s a link to this dev_topology in Excel.

 

Service Category Server1 Server2 Server3 Server4 Server5 Server6
Cloudera Mgr Cluster Mgt Alert pub Server Host mon Svc Mon Event Svr Act Mon
HDFS Infra Namenode SNN/DN/JN/HA DN DN/JN DN DN/JN
Zookeeper Infra Server Server Server
YARN Infra Node Mgr Node Mgr JobHist Node Mgr RM/NM
Redis Infra Master Slave Slave
Hive Data Hive server Metastore Hcat
Impala Data App Master Cat Svr Daemon Daemon Daemon
Storm Data Nimbus/UI Supervisor Supervisor Supervisor
Hue UI Server
Pentaho BI UI BI Server
IP ADDRESS
AWS details              
Name m3.2xlarge m3.2xlarge m3.2xlarge r3.4xlarge r3.4xlarge r3.4xlarge
vCPU 8 8 8 16 16 16
Memory (Gb) 30.0 30.0 30.0 122.0 122.0 122.0
Instance storage (Gb) SSD 2 x 80 SSD 2 x 80 SSD 2 x 80 SSD 1 x 320 SSD 1 x 320 SSD 1 x 320
I/O High High High High High High
EBS option Yes Yes Yes Yes Yes Yes