HA-OSCAR: the Birth of Highly Available OSCAR
One important factor to consider is the time it takes to build, boot and have the cluster ready to service requests. This is not a major issue for small clusters, but as we move to large installations of 256 nodes and higher, having the capabilities of installing and booting all cluster nodes in an automated and timely manner becomes an asset. HA-OSCAR is considering implementing hierarchical clustering by dividing the cluster into multiple zones. This type of experimentation also can be helpful in identifying the slow processes in the system installation procedure, which allows us to bring it up to speed. LinuxBIOS, for instance, can be included in place of the normal BIOS—with a little bit of hardware initialization and a compressed Linux kernel that can be booted from a cold start—to achieve faster startup times. The upcoming OSCAR release uses multicast technology, which was tested on about 500 nodes, to speed up install times and return impressive numbers. HA-OSCAR plans to adopt this method as the base install mechanism and improve on it.
Similar to the base OSCAR installation, users of HA-OSCAR have the freedom of deciding which application packages to install. By default, HA-OSCAR automatically installs the essential parts to build a cluster and then prompts the user to select the applications they want.
The installation procedure takes into consideration any existing configuration and the packages already installed on the node. Some packages are sensitive to certain system libraries, such as glibc. Users should be aware that installing HA-OSCAR may require them to upgrade their systems based on such dependencies. In the same manner, a de-installation procedure is provided to clean up every HA-OSCAR-specific addition without disturbing the system integrity. This option is important for users who want to test only HA-OSCAR.
It is also worth mentioning that package install and uninstall options are available in the base OSCAR release since v2.0, and a newly enhanced version is coming out soon.
HA-OSCAR plans to investigate the possibility of providing mechanisms for selective network software upgrades without bringing down the system. Network upgrades are an interesting way of patching an operating system and its applications. As an example, most Linux distributions now come with an automatic network upgrade that eases this tedious administrative task. In the case of administrating a large cluster, HA-OSCAR users can use such a feature to upgrade their application version seamlessly, without service interruption. Network upgrade simplifies cluster administration and promotes better software management across all computing nodes.
In addition, HA-OSCAR provides a tool that allows users to change the configuration of the cluster at runtime by using a tool somewhat similar to LinuxConf. This is still a basic idea that will be investigated further in the near future.
Generally, one cannot trust a computing system if there is no backup or recovery mechanism. For mission-critical applications, including telecom applications, it is important to be able to recover from any software or hardware failure. Thus, providing efficient backup and recovery mechanisms is an essential part of any HA system.
In case a disaster occurs, recovery ability and speed are critical. Every time HA-OSCAR is completely re-installed or the kernel updated, ghost images of before and after are saved in a designated location on a backup server and tape. Ghost for Unix takes a snapshot of an old and new kernel, gzips it and sends the image to the secondary head node as well as to a predefined disaster recovery site. Important data as well as application and configuration files also can be included in the ghost image. Normally, tape backup schedules include nightly snapshots for incremental images and weekly snapshots for full images. For faster recovery and highly reliable backups, ghost imaging, file journaling and data replication are implemented.
One goal of HA-OSCAR is to be deployed optionally as a Web server cluster providing highly available Web services to a large number of clients. One step toward this goal is to set up a Web server, such as Apache, on every node; Apache can be one of the packages copied to the nodes. Then, a single IP interface is provided for the cluster, possibly using LVS Direct Routing, because it has proven to be the scalable implementation.
|Dynamic DNS—an Object Lesson in Problem Solving||May 21, 2013|
|Using Salt Stack and Vagrant for Drupal Development||May 20, 2013|
|Making Linux and Android Get Along (It's Not as Hard as It Sounds)||May 16, 2013|
|Drupal Is a Framework: Why Everyone Needs to Understand This||May 15, 2013|
|Home, My Backup Data Center||May 13, 2013|
|Non-Linux FOSS: Seashore||May 10, 2013|
- RSS Feeds
- Dynamic DNS—an Object Lesson in Problem Solving
- Making Linux and Android Get Along (It's Not as Hard as It Sounds)
- Using Salt Stack and Vagrant for Drupal Development
- New Products
- A Topic for Discussion - Open Source Feature-Richness?
- Drupal Is a Framework: Why Everyone Needs to Understand This
- Validate an E-Mail Address with PHP, the Right Way
- What's the tweeting protocol?
- Tech Tip: Really Simple HTTP Server with Python
- BASH script to log IPs on public web server
3 hours 52 min ago
7 hours 28 min ago
- Reply to comment | Linux Journal
8 hours 53 sec ago
- All the articles you talked
10 hours 24 min ago
- All the articles you talked
10 hours 27 min ago
- All the articles you talked
10 hours 28 min ago
14 hours 53 min ago
- Keeping track of IP address
16 hours 44 min ago
- Roll your own dynamic dns
21 hours 58 min ago
- Please correct the URL for Salt Stack's web site
1 day 1 hour ago
Enter to Win an Adafruit Pi Cobbler Breakout Kit for Raspberry Pi
It's Raspberry Pi month at Linux Journal. Each week in May, Adafruit will be giving away a Pi-related prize to a lucky, randomly drawn LJ reader. Winners will be announced weekly.
Fill out the fields below to enter to win this week's prize-- a Pi Cobbler Breakout Kit for Raspberry Pi.
Congratulations to our winners so far:
- 5-8-13, Pi Starter Pack: Jack Davis
- 5-15-13, Pi Model B 512MB RAM: Patrick Dunn
- 5-21-13, Prototyping Pi Plate Kit: Philip Kirby
- Next winner announced on 5-27-13!
Free Webinar: Hadoop
How to Build an Optimal Hadoop Cluster to Store and Maintain Unlimited Amounts of Data Using Microservers
Realizing the promise of Apache® Hadoop® requires the effective deployment of compute, memory, storage and networking to achieve optimal results. With its flexibility and multitude of options, it is easy to over or under provision the server infrastructure, resulting in poor performance and high TCO. Join us for an in depth, technical discussion with industry experts from leading Hadoop and server companies who will provide insights into the key considerations for designing and deploying an optimal Hadoop cluster.
Some of key questions to be discussed are:
- What is the “typical” Hadoop cluster and what should be installed on the different machine types?
- Why should you consider the typical workload patterns when making your hardware decisions?
- Are all microservers created equal for Hadoop deployments?
- How do I plan for expansion if I require more compute, memory, storage or networking?