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Release 1 Linux-HA Fact Sheet

Linux-HA provides basic high-availability (failover) capabilities on a wide range of platforms, supporting many thousands of mission critical sites all over the globe.

Hardware Requirements

Supported Processors

Linux-HA is used on a huge number of platforms, ranging from ARM processors through mainframes. We test extensively on ia32 platforms (8 hours to 5 days), and perform basic testing of each release on every platform supported by SUSE Linux:

• ia32, ia64, amd64, PPC, zSeries mainframes

Beginning with release 2, we have extended our exhaustive testing procedure to OpenPower platforms.

Linux-HA is portable to many platforms, and we treat portability bugs seriously. Patches to fix portability bugs are welcomed.

Data Sharing Arrangements

Linux-HA has no special shared disk requirements.

It supports the following data sharing configurations:

• no shared data

• replication (DRBD, or application-specific)

• SCSI RAID controllers supporting clustering (IBM ServeRAID, ICP Vortex)

• External RAID units - SCSI, Fiber Channel - any kind.

The only requirements we have on shared disk is that it support mount and umount. More specifically, it does not rely on SCSI reservations (or their equivalent).

Supported Software Platforms

Linux-HA is highly portable, and runs on many platforms. It is best supported (and works best) on Linux - virtually any version. The build system creates RPMs and Debian packages automatically, and it is also integrated into the Gentoo Linux build system, among others. Linux-HA is provided natively with SUSE Linux, Conectiva Linux, TurboLinux, Debian, Gentoo and a few other Linux distributions, and is a standard part of many Linux-based products.

It also works completely on FreeBSD, and Solaris.

RAM Requirements

Heartbeat will run in whatever memory your OS and application needs plus about 3 megabytes more. Although it is very lightweight, Linux-HA locks itself and its libraries into memory.

Software Requirements

Special libraries

The RPMs document this best. And, if you don't want to install some of these libraries, then many of these dependencies can be automatically eliminated by rebuilding from source. The only two slightly unusual mandatory dependencies are glib (currently 1.2), and libnet >= 1.1.

The STONITH plugins create a variety of dependencies on the libraries they need - but you don't actually need most or any of them for any given installation, and Autoconf will not create modules you don't have the libraries for.

Kernel Versions

Linux-HA will run on any kernel that doesn't have a major scheduler bug.

For Linux, that means basically anything but Red Hat 2.4.18-2.4.20.

It has no kernel dependencies or hooks.

Miscellaneous

Maximum number of nodes?

For the 1.x releases, the maximum number of nodes is two. Version 2 has multi-node support (tested with 16 nodes).

Are there any Administration-Tools included?

Heartbeat currently comes with the following adminstrative tools:

• hb_standby put current node into standby mode

• hb_takeover put other node into standby mode (in 1.3.0, 1.2.1)

• cl_status provide status information through a command line tool.

Monitoring-Function?

Heartbeat monitors node death, and IP connectivity through ipfail. Version 2 includes built-in resource monitoring. At the current time, many people use mon to handle additional monitoring.

Supported Applications

Linux-HA can support virtually any application that can withstand a crash and be restarted robustly every time, and which can somehow access a good copy of its state data from either machine.

People do a huge variety of things. If you want it, someone has probably already done it. It supports most applications immediately without writing any scripts. See our SuccessStories page for information on how a few selected reference customers use Linux-HA.

Automated Notification when one node fails?

Linux-HA provides configurable automated notification whenever resources move from one machine to another, through the MailTo resource agent. You can easily write your own if you don't like ours. Additionally, you can run an SNMP agent which will send out SNMP traps when nodes fail.

Performance

Which part of Processor-Performance is used for managing the cluster ?

Linux-HA's processor usage is usually negligible, typically much less than 1 percent. If you configure ultra-fast failover times (< 1 second), then this amount will go up with the required faster heartbeat rates.

Which level of availability is reachable?

This is a difficult question to answer since it depends on where you start. As a rule, good HA systems add about one "9" to your system's availability, when appropriately configured. This general rule applies to Linux-HA as well. That is, if your pre-HA clustering availability was 99.9%, then the resulting availability of your system ought to be something like about 99.99%. One can improve on this through good adminstrative procedures and higher degrees of redundancy.

How fast can it detect node failure

When properly configured, Linux-HA can detect failure in less than a second. It is fairly common that people configure a failure detection time of a few seconds.

Administration

Monitoring-GUI

Linux-HA version 1 does not have a monitoring GUI. Starting with release 2.0.5, Linux-HA comes with an easy to use GUI for configuring, monitoring and controlling it.

You can monitor Linux-HA through SNMP using your favorite SNMP-enabled systems management tool.

Command to Execute commands on all nodes simultaneously?

Linux-HA does not provide one at this time, but you could add one easily if you felt strongly about it. It would take around 30 lines of shell script.

Since ssh does such a good job, and the security implications are significant, we haven't yet been motivated to provide such a facility.

Remote Administration of nodes?

You can remotely administer nodes with ssh or Webmin. Webmin has a Heartbeat module.

Rebooting a node remotely?

We support rebooting supported through STONITH plugins which we provide. Appropriate hardware is required.

Function to distribute software to all nodes of the cluster?

No.

See Also

Release 2, Release 2 Fact Sheet

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