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RE: [Linux-cluster] HA Clustering - Need Help



Hi
 
what I can recommend ( in short ) is a RHEL4 U4+ / GFS  Cluster. When you mount the same File system ( in the same time ) on more than one Node you need a Clusterfilesystem ( like GFS or maybe ocfs2 )
 
Example Config:
 
RHEL4 U4 / GFS with DLM and Quorumdisk ( when you only have 2 nodes ) also very Important is the fencing method ( we use now the iLO interface from our HP Servers ). And for the Cluster interconnect I recommend you a separate Network. For the Multipath connection you can use the device-mapper multipath tools ( comes with RHEL4 U4 ) or you use the Vendor specific Driver, like the Qlogic Driver from HP in our Case. When you don't have a Storage box with integrated ( what i think is the best solution ) then you can also use the lvm mirroring. See also the presentation from Heinz Mauelshagen( http://people.redhat.com/~heinzm/talks/MassenspeicherUnunterbrochen.odp in German, maybe he has a English one )
 
Also you should always use a odd number of member (like 3,5,7,...), because the fencing is then better. But when you have a real HA Solution, in the most of the Time you have also Two Datacenters. And then the Cluster should also work when one Datacenter is not available. Then you need either a new Datacenter ;-), for the third member or you fail back to the Problem with the fencing! And then maybe the quorum disk is the best solution.
 
We have around 20 RHEL4 / GFS Cluster in HA Configuration ( also with two Datacenters ), but without quorum disk ( was not available in U3 ). We use on all our Cluster the Shared Root Extension from Atix ( http://www.opensharedroot.org/documentation/the-opensharedroot-mini-howto/ ) because we come from the TruCluster / Tru64 Side and like the Shared Root approach.
 
The last tip from me is, write a test plan and on every configchange you can check your Installation again.
 
I hope this help
 
good luck
 
Mike


From: linux-cluster-bounces redhat com [mailto:linux-cluster-bounces redhat com] On Behalf Of Net Cerebrum
Sent: Dienstag, 23. Januar 2007 18:34
To: linux-cluster redhat com
Subject: [Linux-cluster] HA Clustering - Need Help

Hello All,

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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