[Linux-cluster] General 2-node cluster questions

[Riaan van Niekerk]

Brad Filipek wrote:
> I am in the process of setting up a 2-node cluster with a SAN for data 
> storage. I have a few general questions as this is my first time using 
> RHEL CS.
> 
>  
> 
> I have two boxes with RHEL4U4 and one application. Should the app be 
> installed locally on both nodes, and have the data on the SAN? Or should 
> the app and the data both be on the SAN? This will be an active/passive 
> config.
> 

It is up to you to decide if you want the app on the SAN or not.

App locally installed

If the App is simple and/or part of the OS FS hierarchy (e.g. apache, or 
not in /opt), you can install/configure it on node1 and copy the 
configuration across (keeping in mind that you need to manually keep the 
configs in sync)

App installed to shared storage

(for illustration purposes I will use Oracle as the clustered app)

If the App is complex and goes into a distinct directory you can 
partition off (e.g. ORACLE_HOME somewhere in /opt/oracle), it might make 
more sense to have the whole /opt/oracle on the SAN aswell.

Any files that belong to or are required by the application (e.g 
/etc/oratab, initscripts) would have to be copied across manually from 
one node to the other. If you don't have an easy way of determining 
which files are located outside of the shared partition, you might have 
to install the app twice (once on each side), but it might get confused 
on the second node since it may get confused by the install done on node1.

>  
> 
> Also, does the app and data both need to sit on a GFS?
> 

For active-passive: they don't need to, but they can be. If you are 
using an active-passive cluster and only one node at a time will have 
the application running (and writing to the partition with the data on), 
you can use ext3.

Ext3 is a lot faster than GFS since it does not require the 
overhead/complexity of a clustered file system.

also - a tip - before you configure the app as a clustered service in 
rgmanager, make sure that it starts up flawlessly on both sides (after 
manually moving the VIP and filesystem resources from one node to the 
other). Otherwise, after you configure the app in rgmanager and things 
dont work, you may have to troubleshoot both the app startup and rgmanager.

greetings
Riaan
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