Back in the Oracle 9i days, I was one of those people who got on eBay to buy firewire PCI cards and disks that could do non-exclusive login. Remember that? The first time a little test cluster could be cheap enough for the home enthusiast? I still have the parts in my closet.
Of course, we all know what happened after that – virtualization. It didn’t take long before my home-built test clusters were running on VMware. (Personally, I think that virtualization really started because of those NES and SNES emulators. Most great achievements start with a geek who wants to play more video games.) There are lots of people now who run RAC on virtual environments and it’s easy to find tutorials on the web for many different OS and VM combinations.
Low-Memory Linux
Something I haven’t seen many other people do is RAC with a very small memory configuration. Like 760M of memory per server. (!) Of course you’d only do this for a hobby setup – never on a system where you want any kind of support. But I’m kinda cheap… and running RAC on these small VMs means that I don’t have to go buy an expensive new home computer. My current gateway laptop with Vista Home does the job quite nicely!
10.2 and 11.1 RAC will install and run on servers with 760M of memory. But things were a little unstable at first. Now I’m the curious type… I like to fiddle with things… so I investigated a little bit.
Basic Unix Investigation
There are two basic investigation scenarios:
| what happened in the past | My main tool is sar (System Activity Reporter). Or Java-based ksar on my desktop – it gets data via ssh and graphs it. |
| what is happening now | My starting point is vmstat and top. To dig a little deeper, I might then use other tools like ps, free, iostat or netstat. |
In this particular case, I noticed pretty quickly from the top utility that one process was consuming over 30% of the system’s memory! » Read the rest of this article «