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Don Burleson Blog 







VMware: True RAC Setup Preparation

Oracle Tips by Burleson Consulting


There are two key differences to address during the configuration of your virtual host machines for a true RAC setup. First, there will be multiple virtual hosts that require both a coherent and coordinated setup with your usual minimal installation goal at heart. And second, that this is your first configuration recipe where it is for much more than just simple demonstration purposes. One would likely only incur such added premium costs and additional setup complexities for a real-world test or production database. Therefore, you need to more carefully plan and define your underlying or foundational architecture so as to maximize both its effectiveness and efficiency. It should come as no surprise that this genuine or real world database virtualization project requires something more than freeware.

As such, I must strongly recommend that any virtualized database environment be built using VMwares ESX Server product line their true enterprise scalable, bare metal hypervisor solution. Reviewing the comparison from chapter 2 shown in Figure 4 (next page), ESX essentially provides a pre-canned mini-OS/hypervisor combination that has been streamlined and optimized for large scale virtual deployments. Moreover, VMware ESX provides several features that examines what a virtualized Oracle RAC database requires and for which there may well be no other or easier solution. Plus, it removes one extra layer of overhead, i.e. the host operating system, from your technology stack

Figure 4:  Paravirtualization and Full Virtualization

There are many other advantages to VMware ESX Server over the free GSX Server. ESX Server is more scalable in terms of CPU and memory and also runs faster, which permits more virtual machines per host. Furthermore, ESX Server offers versions that support many extended enterprise requirements such as VMwares VMFS cluster file system, high availability, disaster recovery, and backup/recovery, as this VMware edition feature comparison from their web site shows on the next page (Figure 5).

Figure 5:  VMware Edition Comparison Chart

As with any complex technical undertaking, another primary critical success factor is access to the proper knowledge. Many DBAs will often purchase books to support their project needs. So an Oracle Linux DBA might buy some Oracle DBA books, a Linux reference and possibly a book on tuning Oracle for Linux. There would be nothing special about this practice. So it should come as no surprise that I strongly recommend adding a couple of VMware books to your wish list. Two books that I have found invaluable are:

  • VMware ESX Server: Advanced Technical Design Guide [ISBN 0-9711510-6-7], an invaluable reference text for all things related to VMware Server configuration & tuning

  • Robs Guide to Using VMware, 2nd Ed [ISBN 90-808934-3-9], a concise and informative best practices and general advice book

Finally, be prepared to apply many new techniques in the virtualized world and dont be afraid to make a few educational mistakes along the way!

Special Note:  As with the prior chapter, I am only going to focus on those items of major significance from the prior two chapters, as it relates to configuration and setup.

VMware Host Settings

While the ESX Server host setup may offer some additional challenges that I will not cover here, the two issues of paramount importance relate to the hosts network setup. Looking at the RAC overview diagram on the following page in Figure 6, you need at least two, if not three, distinct network segments. So how do you separate the RAC clusters public, private and storage network segments? Also, how does one bridge or bind multiple network cards together to increase overall bandwidth? There has really been nothing seen so far in the free VMware Server to accommodate these needs and this is why you must upgrade to VMware ESX Server for success.

Figure 6:  RAC Overview Diagram

VMware Server ESX offers a feature called virtual switches to address the network segment separation issue. Network segments can either be separated using VLAN segmentation (as with physical switches) or by simply defining dedicated virtual switches for each different network segments need. VMware ESX Server also possesses a feature called NIC Teaming that combines physical network adapters to support the virtual switches. It is very much like what Linux refers to as bonding and Windows as bridging.

So now let us examine how just one physical database server has to be configured to host two individual instances from two different RAC clusters (Figure 7). Assume that you have chosen to do three network cards per RAC database instance - one for the public network and two teamed ones for the private network - since you know that interconnect traffic and latencies are critical to RAC performance. Thus, just counting the network entities alone on this one physical server, you would have to configure sixteen different items at the hypervisor level. If you then also counted the client operating system network adapters, you would now have some twenty network items per node. So for a ten node RAC cluster, there would be 200 network items to configure! If you now look back at the cartoon at the very start of this chapter, it should make a heck of a lot more sense now!

Figure 7: An Example of Hosting Scenario

This is an excerpt from
Oracle on VMWare: Expert tips for database virtualization by Rampant TechPress.


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