asked
Virtualization (SQL Server on VM). I am soo confused.
here is the question brothers, that I cannot form an opinion on: \--------------------------------------- VIRTUALIZATION: a tricky thinng. How does it work in such scenario as this: someone connects directly to a Virtual Machine. Then may be someone else does too.l not via host but directly. at the same time I am at HOST, also working on same virtual machine. in a situationi like this, isn't it obvious that resources will run out pretty soon? if YES, then HOW IN THE WORLD IS IT POSSIBLE to troubleshoot the situation? or to analyze for performance? or to figure out that the multiuser connections to a VM is actually the culprit of the entire server screwup? [ I tried to read/research, but could not find anything comprehensible or making sense related to the described scenario. Or should such scenario just be PREVENTED and /or avoided by all means? :) if i am at host and say some heavy operations are conducted at host as well, my host starts hanging, then how do i know (or based on what can assume) that a few more folks are connected to the VM and THEIR work is what is causing my host fail? everyone, even experienced net admins or infra. specialists, says MY BEST GUESS is such and such, but we do not know.. (regarding the above questoin). and I have just built 10 VMs on one server, powerful host, etc. but even if one persone at a time uses all of them simultaneously, the HOST server will be shut down I believe. HOW should I handle that, provide for that, or know for sure?..
Just because the net admins you spoke to were experienced doesn't mean that their experience is in virtual machines/infrastructure. All "enterprise" virtual machine host systems (e.g. VMWare) have a variety of tools to monitor and control the guest machines that they are hosting. If you speak to a VM-Admin (who has had the training/has the experience) they would be able to explain the way that their brand of host works and how to troubleshoot performance issues. To learn about VMWare management, I suggest starting with google/youtube/etc. and search for tutorial videos. After that, consider proper training.
The VMWare client is pretty good for getting host and guess counters, so I would start there if your servers are hitting perf issues. Especially if the host has many guests. If the VM metrics are "normal" then start looking at the guest WMI counters (check brents blog for advice) and SQL's own DMV's. I personally dont have an issue with VM, but that is because I have good, VM admins, SAN admins and I know enough to suggest to each one of them a potential bottle neck in their area... Enjoy and Embrace ;-)
If you are connected to a guest, you have no direct insight into the resources of the host or other guests, so you cannot tell that it is another guest that is using the host resources (and causing your guest to operate slowly). At the host level, you can monitor the resource usage of each guest to identify which guest is consuming the host resources. Once you have identified the resource intensive guest, you can log into the guest to see which session or process is consuming the guest resources, if you choose to troubleshoot to that level. The hypervisor, running on the host, also allows you to place constraints on the resources that a guest can consume so you can prevent a guest from overly degrading the performance of the other guests. You always leave some extra resources so the host itself can always function (similar to assigning SQL Server memory and leaving some for Windows). We run dozens of well-utilized guests (sometimes with dozens or hundreds of connections each) on each of our virtualization hosts and have not run into the situation where the host itself became inoperable. We have taxed the hosts to the point where the guests have slowed down, but never to the point where the guest was unusable.
I would suggest that you also have a look at Brent Ozar PLF's next webinar, wherein Brent will be presenting an overview of Virtualisation. There's also a series of Virtualisation vids available on their site at
