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Re: [Qemu-devel] When does live migration give up?
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] When does live migration give up? |
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Date: |
Wed, 04 Sep 2013 19:07:53 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 |
Il 04/09/2013 17:24, Alex Bligh ha scritto:
> We have seen a situation when migrating about 50 VMs at once where some
> of them fail. I think this is because they are dirtying pages faster than
> they can be transmitted.
No, migration never "gives up". It may never converge, but it keeps
trying until cancelled.
Could it be that you are choosing migration server ports from a small
range, and some of them are failing because two migrations pick the same
random port for the destination (which is where the server socket lies)?
Paolo
> What algorithm controls when migration fails in this way, and is it
> tunable?
>
> I am fully aware one answer to this question is "do not attempt to
> migrate 50 busy VMs through a single 1GB/s NIC".