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Oracle

Posted Aug 2, 2007

Oracle RAC: How shared storage works on VMware - Part 3

By Tarry Singh

Brief intro

In our previous article, we looked at the clustering possibilities on the ESX Server. In this article, we will take a detailed look at the various possibilities for building clusters across several physical ESX hosts. We will also look at the clustering possibilities across ESX hosts and physical machines.

Clustering Oracle RAC Virtual Machines across ESX hosts

Here we will create and customize the first node, create and customize the second node, and add shared disks and network configurations. The first step of creating the machine is very much similar to the last article, see diagram 1 of creating a VM.

  • You will create a VM, add two network adapters and local storage for booting and swapping (I personally add two local disks on SCSI0, my first controller. One for boot, I just customized it and put everything under / ; this is a typical 10G disk and a 4G disk for swap) and then go ahead and install the operating system (Windows, Linux or Unix-Solaris).
  • The second node is created much the same way as the first one.
  • Adding shared storage: Here we add remote disks on a new SCSI controller, it is normally SCSI1. Then we go about configuring the IP addresses. You can do that in advance as well. Just watch out for the Solaris 10.3 where my NICs vanished after I added shared storage. In this case, it might be wise to configure the ip addresses at the very end. The disks must point to SAN LUNs. RDM or Raw Device Mapping must be in physical compatibility mode.

For the sake of repetition, we will quickly go through the steps of creating the first node:

  • I normally make resource pools and set all the shares (CPU, Memory) to normal. Please refer to the ESX administration manual for more details on resource pools. It is an excellent means to allocate VMs to resource pools. If you don’t want resource pools, you can just select your ESX host and start creating your VM on it.
  • Datastore: Choose for a local datastore. You can create disks in advance and then allocate the *.vmdks to the newly created VM. You can also create them via the “create VM wizard”.
  • Guest Operating System (OS): I normally have a separate LUN reserved for VM templates and ISO disks. Here I select the OS I need to install. If you already have Virtual Center then you can just create VMs from ready-baked VM templates. Should you not have the templates, just go ahead and install the OS.
  • CPUs: Choose as many vCPUs as you need.
  • Memory: Depends on how much you have on your ESX server. I prefer to keep them to 2G per VM but you can also try on 1G per VM. Just make sure to tune your Oracle Memory management manually.
  • Network Interface Cards (NICs): Create two of them.
  • Click OK and create your VM.
  • After creation, do the necessary post creation tasks such as configuring your floppy, CD drive etc.
  • Installing Guest OS: We pointed our Cdrom to the ISO files of our OS. Now its time to install it. Select the VM and in the CD drive setting, check the boxes to be “connected”. Now, power on the Virtual Machine, and continue with the installation. For Linux we have detailed our installation of RHEL as well as Oracle Enterprise Linux. Please follow those steps carefully as documented and you will have a successful installation.

Now let’s see what we need to do to create the second node. The best way is to clone the machine you just created. (Why go to all the trouble to make machines.) If you are to test an 8 Node RAC on your ESX, you might as well go ahead and do it smartly. That is why VMware ESX Server is such an exciting platform to work on.

  • Shut down node 1 and power it off.
  • In your VI client, select the VM01 (we will call it VM01 and VM02 for the sake of simplicity) and right click to clone it.
  • Name/Location: Choose VM02 and the Datastore where both nodes should be stored as per your capacity planning.
  • Host or Cluster: Choose the second ESX host (let’s call it ESXRAC02) for cluster setup.
  • Resource pool: Select a resource pool, if you have created one or just add the machine to that new ESX host, ESXRAC02.
  • Datastore: Choose local datastore. In any case, make sure that you have enough space to accommodate the new VM.
  • Do not customize
  • Select OK to create the clone

Note: Many users may not be able to clone or may not find cloning the right way to go. I have a tip for those users. Did you know that you could use the free VMware Converter to clone your VM on your ESX or VMware Server/Workstation? Try it. In another article, we will throw in some screen shots.

Adding Shared Storage

To add shared storage please use the following steps:

  • Select the newly created VM01 or VM02
  • Click Add hard disk and then click next
  • For disk space choose Mapped SAN LUN
  • In the LUN choices, pick up an unformatted LUN (Make sure you are doing all this as your SAN admin) and click next
  • When selecting the datastore, select local datastore and click next. (The RDM mapping is also stored in this location).
  • Select “physical compatibility mode” and click next (You will notice in the edit settings tab that a new SCSI controller SCSI(1: 0) is created when you create your Virtual Hard Disk). Add all the disks to it. Ocr.vmdk, asmfile.vmdk, votingdisk,vmdk, asm01.vmdk, asm02.vmdk etc.
  • Select new virtual device node and choose the SCSI1:0, SCSI1:1, SCSI1:2, etc. for all your RAC files.
  • Click Finish to create all the disks.
  • Select this new SCSI1 controller and change the controller type to LsiLogic
  • In the same panel, change the SCSI Bus Sharing to Physical (as in the print screen below).
  • Click OK (As mentioned in my previous article, when starting my VM, I once got a few dialog boxes asking me to change the type to LsiLogic. I acknowledged all the messages.)
  • Do the same steps for VM02 node. All you have to do in this case is to point to the “existing vmdk” created from our above-mentioned steps. Allocate the SCSI1:0, SCSI1:1 etc. to the disks in the same manner as you did with the VM01 and now you have a fully configured multi-ESX host Oracle RAC cluster ready to be installed with the RAC software.

After the multi-host configuration, your configuration will look like this (courtesy VMware Documentation):

Here the remote storage is your SAN or NAS. FC or Fiber Channel is used for SAN and you will also have additional HBAs per ESX host.

Conclusion

In the next installment, we will explore the Shared Storage considerations where one node is still on a physical machine and the new node is on an ESX host. Are you thinking what I am thinking? Yes indeed, migrating your Oracle RAC from physical to virtual might just be a matter of deleting physical nodes while you are adding new nodes on the ESX host! You can do it all yourself!

» See All Articles by Columnist Tarry Singh



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