Monday, 16 September 2013

XenServer Networking

There remains much confusion about what is management interface; what it does and how should we go about configuring networking for the enterprise. Below is a brief discussion about it :-
We can break XenServer networks into three brands :-
Management Interface
VM Networks
Storage Networks

Please note that each one of them is entirely different in their working and hence should be differently configured.
Management interface is primarily for your XenServer hosts. It is through this interface that all the management activities of the hosts progress such as :-
+ copying, moving, exporting your VM
+ HA heartbeats
+ Pool consistency check
+ VM management activities such as migration, startup sequences etc..
and many others

This interface being the most important for the working of the hosts should be bonded to have failover if one of the NICs go down. With the latest version of XS i.e 6.2 we can now have four NICs in a bond. Please provide a static IP as a best network policy although we have an option of providing DHCP in management. VLAN tagged network is not supported here

VM Network :- This is the interface where all the network traffic for each individual VM progresses. It should be highlighted here that there were issues reported for offload engines with 2003 VM's (although it is EOL, but VM's already running over 2003 are not going to be migrated to any other Server version all of a sudded ) and therefore they are recommended to be disabled for better performance. Consequently Offload engines are therefore suggested to be disabled at pif level. The NICs can be bonded for network failure and tagged network is allowed here. DHCP can be recommended in some scenarios such as XenDesktop provisioned VM's etc ; it is entirely scenrio based.

Storage Network :- The Storage interface is the one on which storage is going to provision LUN's to the hosts. The same interface is used to have Multipaths enabled. Multipath enabled networks must not be bonded (as we defeat the purpose of multipath by bonding the NICs and also considering the performance is reduced). The storage NICs must be on different subnets and so should be the storage controllers.