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Re: [Linux-cluster] Linux Virtual Server Vs RedHat Cluster

Manilal K M wrote:

Yesterday I came across Linux Virtual Server. I have read the
documents at  http://www.redhat.com/docs/manuals/csgfs/browse/rh-cs-en/pt-lvs.html.
Now I'm confused more ..
Think of Linux Virtual Server (LVS) as a load balancer. You have one (or more) machine functions as load balancer that distributes the load to multiple "real" servers. Usually you need some kind of frontend to LVS, such as piranha or keepalived.

Each one of this "real" server needs to know how to handle the requests in the same way. Usually this means each real server needs to have identical data, either synchronized at application level (the way MySQL cluster does), manually synchronized (e.g. with rsync), or shared data (via NFS or cluster file system). The GFS-part of redhat cluster can be used to provide cluster file system for your real servers, but you should also make sure that your application can operate on shared data without causing corruption. For example, you can have multiple servers running apache accessing the same data/files provided by gfs and it should work OK, but you should not have multiple MySQL server accessing the same files.

Since your priority is HA (which means active-standby configuration is OK), you can simply use redhat cluster without GFS. The cluster suite can provide mechanism for checking your services, and restarting or relocating the service if it fails. This means that if you have only one service, it will only run one node, leaving the other node idle. But if you have multiple services (apache, MySQL, etc) you can distribute the services on both nodes, and if one node fails the other node can take over the services.

If you need HP and HA you can use redhat cluster with GFS to provide cluster file system and run your services on both nodes, but you'll also need some kind of load balancer (such as LVS) to distribute the load between those two nodes.


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