I will take the LPIC304, so I will summarize it. For the LPIC304 exam, please check the Official Page. Since there was a lot of volume for each topic, I wrote it for each unit.
Virtualization is the abstraction of computer resources.
・ Flexible management of H / W assets -Virtual machine template ・ Dispersion of peak hours ・ Reduction of running cost
-Impact of physical server failure and maintenance ・ Performance degradation ・ Requires virtualization expertise
--Host OS type --Features: Install the virtualized S / W on the host OS and run the guest OS on it. --Advantage: Easy --Disadvantage: Increased operation overhead --Specific tools: VirtualBox, VMware Workstation, Microsoft Virtual PC, Parallels Desktop
\ # Only the features of VirtualBox appear in the test
--Hypervisor type --Features: Launch the virtualization software directly on the physical machine and boot the guest OS on it. Mainstream virtualization in the enterprise. --Advantage: Performance is better than host OS type --Tools: Xen, HP's Integrity Virtual Machines, VMware's VMware vSphere
There are two types: full virtualization (also called H / W virtualization) and paravirtualization (PV).
|H/W emulation||To do||do not do|
|Guest OS fix||Unnecessary||necessary|
|CPU virtualization support function||necessary||Unnecessary|
Full virtualization can be used as a guest OS.
To improve the efficiency of full virtualization, use the virtualization support function of the CPU. This is a feature included in modern CPUs. The processing is speeded up by the CPU sharing part of the processing performed by the virtualization software. It is implemented as Intel VT (Intel Virtualization Technology) and AMD-V (AMD Virtualization).
It is possible to provide an independent environment for multiple servers on one physical server without the trouble of creating a virtual machine. It is attracting attention with the development of cloud computing.
It consists of a combination of Linux features. Changes in the root directory location by "chroot", spatial separation by "NameSpace", restrictions on grouped resources by "cgroup", etc. are used. In other words In-container processes can only see the space up to the modified root directory and behave in isolation from each other. By limiting resources in the isolated space, an isolated space suitable for each environment is formed. Looking at each container from the OS side, the container is a normal Linux process, and only one OS is running.
There are LXC, OpenVZ, and Docker as container type S / W.
--Features: There is no need for emulation because there is no virtual H / W concept of virtual CPU, virtual memory, and virtual disk. --Advantage: Fast construction speed. High aggregation rate. --Disadvantages: OS malfunctions and failures are widespread. I can't run a different OS. There are restrictions on customization at the OS level.
The cloud refers to computers and services on the other side of the network. For more information here
--On-demand self-service --You can freely use the services you need when you need them. --Broadband network access --You can access it from anywhere using the Internet --Resource sharing --You can save and use resources --Speedy expansion --You can change the usage of services and resources quickly and flexibly. --Service can be measured --Resource usage can be measured
--Private (in-house) cloud --Community cloud --Public (Internet) Cloud --Hybrid cloud
Moving an existing environment to another environment as it is
--Live migration --Migrate without stopping the service. --One of the attractions of virtualized systems