I am totally new to HA clustering and am trying hard to grasp the fundamentals in a limited time frame. I have been asked by my company to create a high availability cluster using Red Hat Cluster Suite on hardware comprising two servers running RHEL AS 4 and one shared external storage array. The cluster would be running in Active-Active state. Oracle Database version 9 (not RAC) would run on one of the servers while the Oracle Applications version 11 would run on the other. In case of failure of either of the servers, the service would be started on the other server. Both the servers (nodes) would be connected to the storage array through two redundant SCSI controllers.
Since the storage has redundant controllers, both the servers would be connected to the storage array using two channels each and the requirement is to make it an Active-Active Load Balanced configuration using a multipath software. The storage vendor has suggested using the multipath option with the mdadm software for creating multipath devices on the storage array.
I have gone through the manuals and since this is my first attempt at high availabilty clustering I have many doubts and questions. What file system should be used on the external storage ? Is it better to use ext3 or Red Hat GFS ? At certain places it is mentioned that GFS should be used only if the number of nodes is 3 or more and GULM is being used. Since we have only two nodes, we plan to use DLM. It is also mentioned that GFS and CLVM may not work on a software RAID device. Would the multipath devices created (/dev/md0, /dev/md1, etc) be considered to be software RAID devices, though in the real sense they are not ? Further the development team is not too sure about the compatibility between GFS and Oracle Database and Applications. What could be the pros and cons of using ext3 file system in this scenario ?
The development team just wants one filesystem to be used on the storage which would be mounted as /oracle on both the servers / nodes and all the binaries and data would reside on this. Since this filesystem is going to be mounted at boot time, my understanding is that no mounting or unmounting of any filesystem will take place during the failover so the cluster configuration should reflect that. The documentation repeatedly refers to mounting of the file systems when failover takes place so that's giving rise to a little confusion. Further there are references to a quorum partition in documentation but I have not been able to find any provision to make use of the same in the cluster configuration tool.
Please help me in clarifying these issues and suggest me how to go about setting this cluster. I would be really grateful for any suggestions and references.
Thanks,
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