21 Virtualization, Automation, and Programmability Flashcards
Virtualization Components
The components that virtualization solutions rely upon are:
■ Hypervisor
■ Virtualization guest
■ Virtual appliance
■ Virtual switch
■ Shared storage
■ Virtual storage
Hypervisor
A hypervisor or virtualization host is simply the server that runs a virtualization solution. Most of the time, it’s just called “the host.” Typically, the host has lots of computational resources like processors, cores, and memory in order to run multiple virtual machines.
Virtualization Guest
A virtualization guest, or often just “guest,” is another term for a virtual machine that runs on a host. Depending on the exact virtualization solution, a guest can run practically any modern operating system.
Virtual Appliance
A virtual appliance is a virtual solution provided by a vendor. Nearly all vendors provide a virtual option when you buy their product. As for Cisco, they have an arsenal of virtual appliances. The most useful ones to remember objective-wise are:
■ Cloud Service Router 1000v (CSR1000v): A virtual router that runs IOS-XEc software.
■ ASAv: A virtual version of Cisco’s ASA firewall.
■ Firepower Threat Defense Virtual: Virtual version of Cisco’s Firepower firewall solution.
Virtual Switch
All virtualization solutions have a virtual switch (vSwitch) that each host uses. The virtual switch acts just like a regular switch except it doesn’t run STP. vSwitches basically allow hosts to assign VLANs to virtual machines. They can also perform more advanced tricks like trunking and can even support switch features like CDP, LLDP, and SPAN, and security features like Private VLANs. vSwitches tend to come in two forms:
■ Standard: This is the free version switch that offers basic features. With this variety, every host will have its own independent virtual switch, meaning if you configure VLAN11 and VLAN12 on a host’s vSwitch, you’ll need to configure the same VLANs on any new host you add into the network that’ll be sharing the workload. You do this just like you would when adding a new switch into the network if you aren’t using VTP.
■ Distributed : This option creates a single, logical, virtual switch that runs on all hosts. It supports advanced features and shares configuration between all hosts. A distributed vSwitch is just like a switch stack where all switches share the single configuration.
Shared Storage
While you can create virtual machines using a host’s internal storage, this approach is very limiting when growing your virtualization environment because other virtual hosts can’t easily reach the internal hard drive. The most common solution is to use shared storage technologies like accessing a SAN or NAS through iSCSI or Fibre Channel. Doing this permits all hosts in your network to access the same common storage enabling more features, which we’ll talk about a little bit further on. VMware uses a special fi lesystem on its storage wherein mounted paths are called datastores. Since Hyper-V just uses the regular Windows fi le structure, it doesn’t need this concept.
Virtual Storage
Maybe you’re thinking, “okay, you can virtualize servers and networks, but I bet you can’t virtualize storage!” Actually, you can! Just know that storage area networks, or SANs will defi nitely shrink your bank account and they’re complex too. To get around these caveats, the industry has begun embracing Hyper Converged solutions—a solution that combines computing, networking, and storage into a single server. Basically, with virtual storage, each host utilizes its local storage to create a logical SAN across the network, which all the virtual hosts can use as virtual machines. Common solutions for this include:
■ Cisco HyperFlex : This is Cisco’s main Hyper Converged solution that runs VMware or
Hyper-V with virtual storage on its Cisco Unified Computing System (UCS) servers.
■ VMware Virtual SAN : This is a built in VMware solution that provides a virtual SAN
for your VMware hosts.
■ Microsoft Storage Spaces : Clearly a Microsoft solution that provides virtual storage,
which can be generally used.
Virtualization Features
Here’s a list of three components that virtualization solutions use:
■ Hardware abstraction
■ Snapshots
■ Migrations
Hardware Abstraction
You’ll appreciate this one if you’ve built a computer or two because computer hardware can be pretty annoying. Because hardware requires drivers that only might be provided by Windows Update, trying to standardize computers across your company is a bit challenging. There will always be slight differences as computers get upgraded or the manufacture adjusts the hardware components! With virtual machines all the hardware is virtualized, so everything is always predictable even if you move the VM across several hosts.
Snapshots
Snapshots is basically an “undo” button for your virtual machine. It captures the state of a VM before you take on a task and allows you to revert to it if you need to. For instance, it’s a good idea to take a snapshot of a VM before you attempt an upgrade because if the upgrade blows up the application, you can simply revert to the snapshot rather than tangle with manually undoing the upgrade. Backup solutions such as Veeam also use snapshots to create a backup copy of the virtual machine. And of course, different vendors call features by their own names, for example, Microsoft calls their snapshot feature “checkpoints.” Note: Be aware that snapshots aren’t always a magic solution! In the example above, if the failed upgrade also made changes to a database on another VM, that VM would need to have a snapshot as well to fully revert the changes.
Clones
Clones allow you to quickly create a copy of a virtual machine. They’re a handy feature for creating several virtual machines based on a “golden” image that you’ve already patched and configured exactly the way you want it.
Migrations
Virtual machines can be migrated between hosts to balance the workload or ensure VMs are still running if the host needs to shut down for maintenance. This is cool because if shared storage is being used, the virtual machine can be migrated while it’s running to avoid downtime! Otherwise, the VM most likely will need to be powered down during the move. Migrations can be manual or automatic based on performance or host availability. Migrations come in two types:
■ Virtual Machine Migration: Refers to when moving a virtual machine from one host to another.
■ Storage Migration: Refers to when moving a virtual machine from one storage location to another. For example, moving a VM from internal storage to an iSCSI datastore.
Virtualization Types
There are two types of hypervisors available.
Type 1
Also known as a bare-metal hypervisor—when the entire server and OS is dedicated to virtualization, the hypervisor can directly access all hardware on the system. This is the most common enterprise solution since it provides the most features and the best performance. Here are three Type 1 solutions:
■ VMware ESXi
■ Hyper-V
■ Xen
Type 2
Also called desktop virtualization. It refers to when the virtualization solution runs on top of your desktop OS as an application and is mostly meant for IT/developer
testing since it offers a lot less features and performance. You get what you pay for—Type 2
is really simple to use and it’s cheap! These are Type 2 solutions:
■ VMware Workstation/Fusion
■ VirtualBox
■ KVM
Hardware Virtualized
Machine Hardware Virtualized Machine (HVM) refers to when the virtual machine isn’t aware it’s a virtual machine. The hypervisor presents hardware to the VM that it can interact with—a hypervisor will commonly present an Intel e1000 network adapter for network connectivity, which is a widely supported NIC that should be run “out of the box” on most systems.
Paravirtualization
This virtualization type takes advantage of virtualization-aware operating systems. In this kind of system, the guest is “enlightened” to the fact that it’s a VM and directly contacts the hypervisor instead of using emulated hardware. Paravirtualization can give us better performance, but the downside is that the VM needs to support the feature, so it often requires drivers to be installed on the guest operating system for it to actually function.
