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VMware Distributed Resource Scheduler is used for dynamic resource scheduling of server resources. In other words, VMware DRS continuously monitors utilization across resource pools and intelligently aligns resources with business needs by utilizing VMware’s vMotion technology to move virtual machines from a physical host to another physical host. By doing this, resources in a VMware ESX cluster can remain consistent and load balanced across all nodes in the cluster.
This is another prime example of how automation can help the administrators do their day to day job easier and better. There are different levels of DRS automation starting with manual setting and ending with a very aggresive trigger for the automation. The manual setting is where VirtualCenter will recommend migration to take place but will leave the decision to the admin to decide if they want to perform the migration or not. I am not a big fan of this setting except in trouble shooting situations. This is kind of like having a Porsche and not being allowed to drive it. In my opinion why have the technology if you are not going to use it.
Once automation is enabled there is a five star rating system for how active the automation will be. A single star or conservative setting will only attempt to migrate the virtual machine or machines if a major performance increase will happen to the host by performing the migration. At the other end of the spectrum is a five star or aggresive setting. This level of automation will attempt to migrate the virtual machines if the migration will increase, even slightly, the overall performance of the host. That leaves three other settings in between the extremes to choose from.
The question I present is, what do you think is the best setting to run DRS on? At one point I had DRS set on the most extreme five star setting and found what I thought was too many vMotions especially during the backup window when the virtual machines CPU usage would increase to handle the backup schedule. I personally like to try to keep things pretty much even and load balanced across the cluster as much as possible. I have found the four star setting the best for me. Not too ambitious but yet keeps things pretty much even across the board. I would go as far to say that even if that is to aggressive for your taste to at least be ambitious to start until things are load balanced and then tone it down.
This is my opinion, so what is yours?
DRS, VirtualCenter, virtualization, vmware
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This entry was posted on Tuesday, March 17th, 2009 at 4:50 am and is filed under Virtual Tech. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
March 17th, 2009 5:02 am
Because of the application Captiris Alchemy, we have to run DRS with manual settings. Yes, Alchemy has weird licensing that ties it to a specific host and it’s document management services will fail to start if it runs on the “wrong” host.
We have contacted Captiris on this issue several times, and we have one license per ESX host that we’ll have to install manually in case of a host failure. Not an optimal solution, and I hope Captiris will find a better solution to this soon.
Lars
March 19th, 2009 10:55 am
Set it to fully automated and 3/4 stars, I found that 5 was also causing too many Vmotions between the hosts
March 25th, 2009 1:05 pm
5 is definitely over the top. I am running my cluster at 2/fully automated, but even as that is considered conservative I still wonder sometimes how exactly it calculates things and why machines are moving around.
By the way - nice blog with good content, but it is really hard to read white text on black background. You might want to research color schemes a little bit to make it easier for visitors.
March 25th, 2009 8:50 pm
I have found that fully automated and 4 stars works best for me as well. Similar thoughts to what you had in that 5 stars was a little too quick to move things around for short periods of high utilization.
March 27th, 2009 11:34 am
Hello,
All I have done is the default settings for the DRS. However, I’m still confuse about the correct settings for my DRS. I have 4 hosts each , 2 of them with 20 GB ram and 2 single Process 3.0 Ghz. and the other 2 each with 12 GB Ram, and 2 dual-core processor. Total of 74 memory and around 34 ghz CPU.
How best I can make the DRS settings for my VMs? I have around 40 VMs.
Thanks,
S.Hussani
March 27th, 2009 11:44 am
The real answer is going to be “it depends”. What works for you. The default settings are there because it should work for just about all. What are you hoping to achieve or what do you think is not working? 3 Stars is the default I just perfer to be a little more aggressive and this has worked for me quite well.