The IP for a package in Metrocluster

[Michelle_61]

Greetings,

I am new to Metrocluster and need to evaluate this product with our application. My main concern is the IP address configured for a package in a Metrocluster, because our application may have a heavy dependency on the IP that identifies itself. In the Metrocluster I need to configure our application as a package in both data center A and data center B (each locates in different subnet). Is it TRUE that in case of failover the whole package (including the IP configured for it) will be available on the other data center? If so, then what I do not understand is, which subnet should the package IP belongs to? How can I configure the same IP in wo subnets?

Did I miss anything regarding the networking setup in Metrocluster?

Your help will be very appreciated!

[Matti_Kurkela]

The Metrocluster product can use either a single subnet that covers both data centers, or separate subnets for each data center, depending on configuration choices.

But from your description it seems that your application might not be capable of using separate subnets.

If your network infrastructure does not allow for stretching a single subnet to both data centers, you must investigate in detail the nature of the IP dependency of the application.

• Is it because the IP is specified in the application configuration? Some custom scripting in the cluster package startup might fix that.
• Is it because the application license is tied to the IP address? Then you must negotiate with the application vendor.
• Is it because the clients get confused if a different IP address is used? Then you might need some network-layer HA solution in addition to the MetroCluster.

[Michelle_61]

Thanks Matti,

Your suggsetion of using custom scripting in the package startup might work.

I want to pursue more on the case when separate subnets are used for each data center. So in that case I suppose both IPs in the two subnets shall be configured for the package, correct? And the package should be able to be online when either of those two IPs are online? I do not know how MC ServiceGuard allows the package to be fully online when only one of its IPs is online. Could you explain?

Thanks in advance!

[Matti_Kurkela]

Well, the basic Serviceguard has a requirement that all the cluster nodes are in the same network segment. The Metrocluster extends Serviceguard to remove that requirement.

Unfortunately, the Metrocluster configurations I've actually used all used a single network segment, so I'm not really familiar with the separate subnets case. But I would expect some Metrocluster-specific configuration entries that would list a specific IP address for each package+node or subnet+node combination. One thing is for sure: the answer for this cannot be found in the basic Serviceguard documentation. You need to look at Metrocluster-specific documentation to find the answer for this one.

(Or maybe the Extended Distance Cluster documentation, since it seems to be the intermediate step between basic Serviceguard and Metrocluster.)

[Stijn Adriaensens]

Packages in cross-subnet metro clusters have two IP addresses, one for each datacenter. You cannot use the same IP address in different subnets. The package configuration will look something like this:

ip_subnet <subnet in dc1>
ip_subnet_node <nodename in dc1>
ip_address <ip in dc1>

ip_subnet <subnet in dc2>
ip_subnet_node <nodename in dc2>
ip_address <ip in dc2>

Depending on where the package starts, it will bing up the correct IP address. Off course you can do this for more than 2 datacenters.