[CentOS-virt] Live migration using shared storage in different networks

Mon Jul 6 16:58:19 UTC 2015
Mike - st257 <silvertip257 at gmail.com>

On Mon, Jul 6, 2015 at 7:58 AM, Miguel Barbosa Gonçalves <m at mbg.pt> wrote:

> Hi!
>
> I am building a KVM cluster that needs VM live migration.
>
> My shared storage as well as the KVM hosts will be running
> CentOS.
>
> Because 10 Gbps Ethernet switches are very expensive at the
> moment I will connect the KVM hosts to the storage by
> cross-over cables and create private networks for each
> connection (10.0.0.0/30 and 10.0.0.4/30).
>
> The following diagram shows the topology
>
>  Management             Management            Management
>     VLAN                   VLAN                  VLAN
>      |                      |                     |
> +----+-----+  10 Gbps  +----+----+  10 Gbps  +----+-----+
> | KVM Host |-----------| Storage |-----------| KVM Host |
> +----+-----+           +----+----+           +----+-----+
>      |                      |                     |
>    Public                 Public                Public
>     VLAN                   VLAN                  VLAN
>
> My question is: will live migration work in this configuration
> since the storage will have 2 different IP addresses
> (10.0.0.1 and 10.0.0.5) in 2 different networks even though
> it is the same storage?
>

I don't know for sure if you'll run into problems having two different IP
addresses, but I'd suspect you would.
Some people (myself included) on this list use LVM backing and DRBD on the
KVM hosts in which case the referenced storage layer is identically named.

Solution(?) for your scenario:
Maybe create a bridge on your Storage node that includes both 10Gbit NICs
going to your KVM hosts?
That way you put a single IP address on the bridge and it is accessible
(because it's bridged) to both KVM hosts. And less need for a 10Gbit switch
(just yet).


-- 
---~~.~~---
Mike
//  SilverTip257  //
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