Information Technology Reference
In-Depth Information
Cost Evaluation Plug-in Modules.
We have implemented plug-in modules for four
typical VM placement policies. The plug-in modules are written in Ruby 1.8.
1.
Electricity saving
This plug-in module evaluates the cost of electricity. For simplicity, we focus
only on whether a physical server is powered on or off. The actual electricity
consumption depends on the load, but there is a significant difference
between powered on and off.
Evaluated cost will be:
E
, if a VM is placed on a host which needs to be powered on
0, otherwise
{
2.
Availability of a virtual system
This plug-in module takes particular note of redundancy of VMs in the same
tier. An example of a commonly used three-tiered web system is shown in
Figure 3. In the example, each tier (web, application, and database) has
redundant VMs. However, the whole tier will be downed by the failure of a
single host if redundant VMs are deployed on the same host. To prevent such
a situation, this module considers the loss of redundancy as a cost.
Evaluated cost will be:
F
, if a VM is placed with another VM that belongs to the same tier
0, otherwise
{
Fig. 3.
Example of a 3-tiered web system
Fig. 4.
Example of 3 types of communication situations
