VMotion Migration

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Pretty impressed with how quick this is.

Quick question. We did a standard ping -t on one windows server VM today to see how many packets were lost during the migration of another from 'ESX01' to 'ESX02'. Only one was lost!

My lab partner said that in Linux machines you can set it so that it can be reached constantly, and no packets lost....does anyone know if this is possible and how to do it in Linux...also if it is possible to set in Windows?

(not that you'd need it for the migration process, but it would be handy to know for other stuff!)

 

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Was this a silly question? (I did try finding an answer before posting, but wasn't successful)

Perhaps the thread is best placed elsewhere as it is not directly related to Vmotion?!?...

 

I put it to your lab partner that he/she is talking bollocks. The O/S of the VM you are migrating has nothing to do with the VMotion process. The reason a ping or two may be dropped during a migration is pretty simple to understand - once you know how VMotion works.

When an ESX VM is VMotioned to another host the following process (simplified for brevity) happens:

1 - A copy of the VMs config is made on the second host (I.e. the one TO which the VMotion is taking place)
2 - Active memory pages on the original VM are mapped and copied to the second host
3 - If any pages change during this process, a new memory map is created (with just the changes since the original map was created) and copied to the second host
4 - This process repeats until there are no 'dirty' pages left on the first host
5 - At this point the memory copy is finished - i.e. almost all changes have been made to memory pages.
6 - When there is just a tiny amount of memory copying left to do (not sure of the exact figure, but whatever hash VMWare use to calculate this it probably amounts to something that can be calculated as taking less than a second to copy over the network) all processing is halted on the original host and a RARP (Reverse ARP) is sent out to ensure new packets are sent to the correct VM.
7 - The VM is now running on the new host - its this process of incremental memory map copying that ensures downtime is kept to an absolute minimum

However, you will note that there is a point during the migration (step 6) where the VM isn't actually responding to pings - its at this point that there will be packet loss, and you should be able to see that this is utterly independent of the O/S on the VM that's being migrated. You might be able to tune your ping so that it doesn't actually SHOW packet loss - but the packet loss will still be there so that would be pretty pointless!

 

Very helpful as usual (even if it is "simplified for brevity")
The instructor did go through it, but grief! there's a hell of a lot to digest if you haven't been exposed to any of it before ...and hearing the above left me discombobulated.

Thank you Zeb.

 

Har har - I could get uber geeky on yo ass, but that would be sad. Hopefully that's simple enough for most IT people to understand. VI absolutely rules - and VMWare's engineers are some of the cleverest people on Earth, so no matter how I explained it I'd never be able to do justice to their technology!

Are you on the FastTrack VCP course?

 

Uber geeky is good

It's this

It's really just for an introduction to it all, and a case of get familiar with it so I can be called upon in the future if the need arises!!


It's all very exciting stuff though! Hardcore!

 

Yeah, thats the puppy. Prerequisite for the VCP. Are you doing it with Magirus or another TP?

 

PM'd ya

 

Version 3.0?
wtf?

3.5 all the way baby!
just about to throw up some vSphere here at work ;)

 

Hadn't noticed that on the link!

But yeah, the actual course was: "VMWare Infrastructure 3: Install and Configure VMWare ESX Server 3.5 and VirtualCentre 2.5"...and what a course it was! Gonna take a bit of time to get to grips with it all, but well impressed!

 

Ha
you will be a VCP before me



Might tag along on a DSA course we are running for a client later this month, should cover my 'course attendance' requirement

Then I can start working on the VCDX

Glad you liked the course, VMWare is the AwesomeSauce(tm)

 

VCDX? Go you!!