Forgot your password?
New user?
Document Actions
Xen-AoE cluster: A new way to manage servers
How Xen-AoE works and why you want to use it.
[Note: This is a work in progress. Additions will be made as I find time. If you have a suggestion or improvement please leave a comment at the bottom and it will be addressed.]
This paper will discuss the Xen-AoE server technology, how it works, and why you want to use it. We will also discuss the defining principles of what defines a Xen-AoE cluster and why these principles are important to achieving the desired features.
Xen
Xen virtualization technology allows your company to more efficiently utilize your hardware resources. The majority of cpu power on your average computer goes unused. Even on servers the cpu is generally idle the vast majority of the time but still using electricity and producing heat. Your cpu's just sit there waiting for something to happen. Even if we get a web request every second the time between one request and the next is an eternity for a cpu running at 2 gigahertz. But powerful cpu's are needed for those short bursts of activity.
By using Xen to run multiple servers in their own domains (areas of memory) completely isolated from each other on the same physical hardware you can squeeze more utilization out of our existing CPU's/servers. This means we can get by with fewer CPU's, less rackspace, use less power, and require less air conditioning. If your company is concerned about being "Green" or otherwise environmentally friendly or if you are simply concerned about saving on power bills or not needing additional electrical circuits brought into your cabinet in your datacenter a it can be a very prudent move to virtualize all of your servers with Xen.
Energy efficient data centers are in the news again, with the EPA reporting that data centers use 1.5% of US electricity - almost 6 million home’s worth - and doubling in five years.[1]
By encapsulating the servers into this sort of infrastructure it also allows enhanced management capabilities by allowing the administrator to be able to get console access (either text based or graphical) on the server or restart the server while remote instead of having to physically go to the datacenter. This not only saves trips to the datacenter but it also allows the system administrator to easily see what is going on on the console of the system without having to resort to expensive and complicated KVM over IP systems. Xen provides text based console access via ssh and also VNC based console access for full graphical desktop interfaces to the server with any standard VNC client.
AoE
AoE allows us to put a bunch of disk in relatively inexpensive and low CPU powered servers on the network and allow the rest of the servers to access it exactly as if the disk were locally installed in that server. This is advantageous because we can now aggregate all of our disk into one system and treat it like a pool of storage where we can dole out an appropriate amount of disk to each server (often only 10 or 20G is needed) instead of having to put in a dedicated 250G disk which is the minimum you can easily buy these days and waste a lot of disk and power to run it.
The combination of Xen and AoE allows us all of the above plus some interesting fault tolerance abilities. There are now two levels of redundancy in our disk systems and an extra level of redundancy in the cpu's also in that if one cpu fails (or the associated motherboard, RAM, or network card) we can easily switch the servers that were hosted on that machine over to another cpu on the network with either zero or very minimal downtime whereas previously that kind of failure would have required me to drive down to the datacenter and shuffle hardware around or buy new hardware to replace the failed system which all takes time and can result in prolonged downtime.
After a sufficient testing period critical resources such as the database which runs all of ESRP will be moved onto this system to better safeguard valuable company data.
[1] http://www.informationweek.com/story/showArticle.jhtml?articleID=201203026&cid=RSSfeed_IWK_News