But what if one of the system crash and when it comes up all the groups and resources went offline, how would you know on which system it should be online?

So I asked my Team lead and here’s what I’ve learned. There is no primary/secondary concept in VCS but you can mention the priority on which host the service group will come up with AutoStartList and SystemList and it’s more complex than I thought :D

SystemList

The SystemList attribute designates all systems that can run a particular service group. VCS does not allow a service group to be brought online on a system that is not in the group’s system list. By default, the order of systems in the list defines the priority of systems used in a failover. Lower numbers indicate a preference for the system as a failover target.

for example

SystemList = { SystemA, SystemB, SystemC }

configures SystemA to be the first choice on failover, followed by SystemB and then SystemC.

Note that you must define this attribute prior to setting the AutoStartList attribute.

AutoStartList

List of systems on which, under specific conditions, the service group will be started with VCS (usually at system boot). For example, if a system is a member of a failover service group’s AutoStartList attribute, and if the service group is not already running on another system in the cluster, the group is brought online when the system is started.

VCS uses the AutoStartPolicy attribute to determine the system on which to bring the service group online.

AutoStartPolicy

Sets the policy VCS uses to determine on which system to bring a service group online if multiple systems are available.

This attribute has three options:

Order (default)—Systems are chosen in the order in which they are defined in the AutoStartList attribute.

Load—Systems are chosen in the order of their capacity, as designated in the AvailableCapacity system attribute. System with the highest capacity is chosen first.

Priority—Systems are chosen in the order of their priority in the SystemList attribute. Systems with the lowest priority is chosen first.

Example:

In the below example the priority on which group unix1 should be online is at system1

view /etc/VRTSvcs/conf/config/main.cf

group unix1 (
SystemList = { system1 = 0,  system2 = 1 }
AutoStartList = { system1 ,  system2 }
)

system1:# hagrp -display unix1 |grep -i autos
smjrskt1     AutoStart             global      1
smjrskt1     AutoStartIfPartial    global      1
smjrskt1     AutoStartList         global      system1      system2
smjrskt1     AutoStartPolicy       global      Order

I still have a lot to learn and should learn it from scratch, problem is I don’t have much resources

There are a lot of information on the web but the link above was my favorite and I find it very well written.

Here are some of the interesting part, at least for me :)

The first version of UNIX was written in assembly language on a PDP-11/20. It included the file system, fork, roff, and ed. It was used as a text-processing tool for the preparation of patents.

In the early 1980s, Joy left Berkeley with a master’s degree in electrical engineering, and became cofounder of Sun Microsystems (Sun stands for Stanford University Network). Sun’s implementation of BSD was called SunOS.

SunOS was first released in 1983. — we have the same age :D

1993 Sun announced that SunOS, release 4.1.4, would be its last release of an operating system based on BSD. Sun saw the writing on the wall and moved to System V, release 4, which they named Solaris.

As more hardware vendors, such as Sun, began to enter the picture, a proliferation of UNIX versions emerged. Although these hardware vendors had to purchase the source code from AT&T and port UNIX to their hardware platforms, AT&T’s policy toward licensing the UNIX brand name allowed nearly any hardware vendor willing to pay for a license to pick up UNIX. Because UNIX was a trademark, hardware vendors had to give their operating systems a unique name. Here are a few of the more popular versions of UNIX that have survived over the years:

• SCO UNIX. SCO Open Desktop and SCO Open Server from the Santa Cruz Operation for the Intel platform. Based on System V.
• SunOS. Sun’s early operating system and the best-known BSD operating system.
• Solaris. Sun’s SRV4 implementation, also referred to as SunOS 5.x.
• HP-UX. Hewlett-Packard’s version of UNIX. HP-UX 9.x was System V, release 3, and HP-UX11i is based on the System V, release 4 OS.
• Digital UNIX. Digital Equipment’s version of OSF/1.
• IRIX. The Silicon Graphics version of UNIX. Early versions were BSD-based; version 6 was System V, release 4.
• AIX. IBM’s System V-based UNIX.
• Linux. A free UNIX operating system for the INTEL platform; it was quickly gaining a hold in the UNIX community. Versions of Linux became available on Sun, HP, and IBM systems.