Virtualization is a set of techniques that allow multiple operating systems to operate on the same physical machine. Before virtualization, 80% of dataCENTER servers had an average usage rate of less than 10%.
Taking into account technological advances as well as Microsoft recommendations or Linux distributions (one service or one application on the same operating system), it is essential to use virtualization to:
– Make the most of our physical resources
– Reduce the number of physical servers
– Gaining space in our server rooms
– Reduce the time and cost of hardware maintenance
– Reduce our electricity consumption.
Example: Instead of having 10 physical servers in production with a usage rate of less than 10%, we have 2 physical servers hosting 10 Virtual Machines (VMs). Our two physical servers will have a 50% utilization rate.
Our physical servers have 4 physical resources:
– Disc Space
– RAM memory
– Processor (CPU)
– Network card.
We will install on our server our operating system as well as the applications we need (Service Active directory, Antivirus Server, etc…)
So we can schematize it like this:
We've seen that virtualization supports multiple virtual machines. To do this we are going to need a hypervisor.
A hypervisor is an operating system installed on our physical servers. This system will accommodate and run our virtual machines (VM)
There are two main virtualization systems:
v VmWare (ESX)
VmWare is the most used product in the world, so we'll talk about it.
The hypervisor will provide each VM with:
– a percentage of its capacity:
– network access
If we have 10 VMs on our physical server, we're not going to provide a network port for each VM, but we'll provide it with a virtual physical interface connected to a vSwitch."virtual switch.
This vSwitch is capable of tagging Vlan. It will require one or more physical network interfaces with a vSwitch
If we decide to do Vlan marking at the vSwitch level, then we will have to set up a Trunk link between our physical server and our physical switch so that the vlan marking made by the vSwitch is kept in our infrastructure network.
We've seen how our physical servers run our VMs.
If our physical server suffers a breakdown. All VMs hosted by the latter will no longer be executed.
To avoid this, we will put all our physical servers in one Cluster.
A cluster is a working group. All members of a cluster must be exactly the same.
When a physical server fails, the other members of the cluster will retrieve the VMs supported by the cluster and run them until it becomes available again.
To do this, The VMs must not be stored on our physical server, but on a disk bay. That way, each server can run any VM.
To manage clusters, you need the vCenter product.
– ESX: Operating system installed on our physical servers. This system will accommodate and run our virtual machines (VM)
– vSphere Client: Creates, administers and supervises our virtual machines. This app will connect to an ESX or vCenter Server.
– vCenter Server: Allows us to centrally administer our ESX. This Windows service is installed on a dedicated VM.
– vMotion: Allows you to move a VM in operation without a service stop from one ESX to another.
– HA (High Availability): This feature allows you to restart a VM on other ESXs in the same cluster in the event of an unscheduled off-speeding of an ESX. This restart results in a production shutdown, while the VM restarts.
– DRS: (Distributed Resource Sheduler): This feature automatically moves VMs between ESX (via vMotion) to make a load allocation between physical servers.
– FT (Tolerance) : This failure tolerance allows you to run a VM on 2 different physical servers. This VM is executed twice: (A primary VM and a secondary VM, this second VM is the exact copy of the first) In case the host server of the primary VM breaks down, the secondary VM takes over the role of this VM in a totally transparent way without per data or service stops.
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