ServiceGuard Beginners Guide

[Andrew Moody_1]

Greetings.

We are looking to implement a load-balanced with HA environment with 2 rx4640's running RedHat Linux 4AS. This would be to support Oracle 10g Application Server (specifically forms and reports).

Question is, "Is ServiceGuard the way to go?"

[Luk Vandenbussche]

I don't think ServiceGuard is the way to go.
SG is an active / passive environment.
So your application server will always run on one node.

I think it is better to build a pool off application servers.

[Serviceguard for Linux]

Serviceguard itself does not do "incoming" load-balancing. From your question, I think you understand that.

SGLX can obviously handle failover between the two servers. If the same app can have two instances running on the same server, then using Serviceguard might help. If the apps have "intermediate state" state is saved then you will likely get advantage. Consider the following:

If you have an app that has two instances call them APP-A-1 and APP-A-2. They are initially running on two servers with the load balancer "feeding" requests to each. They are saving state on shared storage.

Then the server running APP-A-1 fails. It is then restarted on the other server and recovers some state. Since the "real" IP address for APP-A-1 fails over as well, the client reattaches (assuming it does not time out). You continue on with the client saving the need to re-enter a transaction.


If the senario I describe works in your environment, then you can get an advantage. If there is no state saved or the client doesn't stay attached, then your not likely to get an advantage from an HA failover product like Servicegaurd for Linux.

[Steven E. Protter]

Shalom,

With RH you have the option of using RH clustering as well. I've gotten pretty decent results with it over the past year with seven or eight production clusters at this time.

If you want load balancing you need either a smart round robin dns system that does not hand out dead ip addresses or a dns load balancer. The second option runs between $2,000 and $5,000, but does balance the load.

You may be able to team nic cards with RH NIC bonding. I've never done that with an rx4640 server but its pretty easy with a 32 bit wintel server.

SEP