On Mon, Jul 6, 2015 at 7:58 AM, Miguel Barbosa Gonçalves <m@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).


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Mike
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