L2 in L3 tunneling

為了解決vlan tag只能有4096個(2^12)的問題所以用此方法來解決

L2 in L3 tunneling to the rescue
You want a private L2 network between VMs
You already have working IP between the members of the network
Use that "underlay" IP network and overlay a private ethernet on top

SSH Tunnel

Reverse Tunneling

Unix/Linux: system load

load的就是一定时间内计算机有多少个active_tasks，也就是说是计算机的任务执行队列的长度，cpu计算的队列。


The comparative study of different load indices carried out by Ferrari et al.^[2] reported that CPU load information based upon the CPU queue length does much better in load balancing compared to CPU utilization
http://os.51cto.com/art/201012/240719.htm

http://en.wikipedia.org/wiki/Load_(computing)

bash for-counting-loop

在shell script中

for (( i=0 ; i<5; i++ ))
do
      # do something
done


這種for counting loop是在bash才有 ，sh沒有

Install Quantum on XenServer

For using the quantum plugin see: http://openvswitch.org/openstack/documentation/
You can:

• follow: [[[QuantumDevstack]]]
• ensure your VM network is not on a VLAN
• assuming you use Open vSwitch (default on XenServer 6.0.0 and later)
• run the quantum agent on Dom0
• add in nova.conf: xenapi_vif_driver=nova.virt.xenapi.vif.XenAPIOpenVswitchDriver

TODO - other steps not yet found.