Virtualisation
From Sysadmin
When taking mainframe systems in to account server virtualisation has a long history within the computer industry but it has only recently taken hold within the low cost desktop & server market. VMWare led development within the low cost virtualisation market and found its first significant market with Linux users who wanted to run a virtual MS-Windows system to allow them to run a few applications for that operating system.
With the increasing power of low cost hardware, virtualisation has finally become important to many companies.
Virtualisation can be broadly divided in three categories:
- Full virtualisation
- Paravirtualisation
- Containerisation
Contents |
Full Virtualisation
Paravirtualisation
Containerisation
Advantages
Server Consolidation
The principle of service separation calls for each service or group of related services to be limited by a hard resource barrier. Before virtualisation became common this was most often achieved by allocating a server to the group of services. With the increasing power of servers this has resulted in a large number of servers sitting idle for much of the time.
There was significant waste in:
- Capital cost (purchase price of the servers)
- Management overhead
- Running costs, such as electricity
- Useful for low demand servers
- Eg, web servers, mail servers, irc servers
- DNS can be placed on the host system
- Energy efficient
- Virtualisation is a very green technology
Lower Power Consumption
Services not suitable for virtualisation
Core network services, particularly those that virtual hosts rely on should not be run on a virtual host. Consideration should be given to running at least one nameserver on bare metal.
Services on the Host
It is generally recommended to avoid running services on the host itself as they can be a vector to attack. A successful attack against the physical host will threaten any virtual hosts running on it.
