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Can I increase the number of processors dedicated to my Ubuntu Server 10.04 virtual machine without creating problems to its functions?

It will be accepted without hassle or I should do something at reboot?

If I take a snapshot before that can I be sure to get back to my working 1 cpu configuration?

Thanks, D.

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2 Answers 2

up vote 3 down vote accepted

Go ahead and add the extra CPUs, Ubuntu happily accepts them. Just reboot your Ubuntu server after adding the CPUs.

Please be aware that depending on your application the extra virtual CPUs might not actually help you a lot. Usually yes, but there are exceptions, so please test and benchmark your application extensively after CPU upgrade.

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I run a mysql server on this machine that (only when everyone starts using an application in the morning for 30 minutes) hits 100% cpu use... Will it be useful to add a cpu? –  Pitto Jan 5 '12 at 9:22
    
Just give it a try. :) –  Janne Pikkarainen Jan 5 '12 at 10:00
    
You're right but my hands are always shaking when it comes to "touch" production software / hardware :) –  Pitto Jan 5 '12 at 10:04
    
You'll get over that after enough time has passed, just wait until you earn the BOFH badge. If you don't ever break anything, you have not actually even tried to enhance something. –  Janne Pikkarainen Jan 5 '12 at 10:07

One thing you have to watch out for is that ESXi will not schedule your VM until it can provide all the vCPUsthat you assigned to it. This may lead to your VM having to wait for vCPU resources to become available which man not be what you want.

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I run a mysql server on this machine that (only when everyone starts using an application in the morning for 30 minutes) hits 100% cpu use... Will it be useful to add a cpu? –  Pitto Jan 5 '12 at 9:21
    
I think this has no longer been the case since ESX(i) 4.0. –  ThatGraemeGuy Jan 5 '12 at 10:32
    
From what I've heard it's better in later versions of ESX(i)4.0 or 4.1 but still exists to some degree. –  Keith Stokes Jan 5 '12 at 12:59

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