active-active / active-passive?

[Anthony Baldwin]

Can someone give me a brief explanation of the difference between active-active and active-passive? Thanks in advance. Regards.

Anthony

[James R. Ferguson · Accepted solution]

Hi Anthony:

In High Availability (HA) clusters, "active-active" describes a cluster where several nodes are running critical applications while serving as backup nodes for one other.

"Active-passive" ("active-standby") configurations are those where several nodes are running critical services and others are idle awaiting a failover event. The idle nodes will takeover in the event of a primary node's failure. In some cases, the standby node may be a test system which ceases to serve as a test environment in the event it needs to assume the critical applications of its failed primary.

...JRF...

[A. Clay Stephenson]

Hi Anthony,

This terminology only has meaning if more than one package is involved. Consider a two-node (HostA & HostB) cluster running two instances of Oracle under two packages - PkgA and PkgB.

Active-active mode would have PkgA running on HostA and PkgB running on HostB - thus both hosts are actually running a package but either package can failover to the other node.

Active-passive mode would have both packages running on HostA and HostB would be standing idle but ready to run both packages in the event ServerA failed.

The concept can be extended to any number of packages and any number of hosts within a cluster. Obviously active-active is much less wasteful of resources.

Clay

[linuxfan]

Hi Anthony,

Don't know if you remember HP's SwitchOver, which was before MC-SG. When you use switchover, you configure two machines with exactly the same configuration, and if for whatever reason there is a problem on one, that machine is shutdown automatically and the other (standby/failover) would startup with the same static IP address and everything.
In today's terminology of MC-SG this scenario(with slight differences like the nodes would have their own static IP addresses) would be known as active-passive.
This has certain disadvantages in the sense you are not utilizing all the resources, you have one complete system sitting idle doing nothing but waiting for something to go wrong on the other machine(well in the real world one hopes nothing should ever go wrong)

On the other hand active-active is a situation where you have applications running on both the nodes and you are making full use of the computing resources of the machines. Not only are you using your resources but are making it redundant using the MC-SG because if forever reason if something goes wrong on one node, your application would be back up on the failover node (also known as stand-by node).

-HTH
I am RU

[Anthony Baldwin]

Thanks guys. That was helpful. It sounds like active-passive = active-standby. I didn't realize that.

Regards.


Anthony

[linuxfan]

Hey Anthony,

thanks for the points, but i just missed my first hat, by 1 point.

:)

-Regards
I am RU