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By Bhanu P Tholeti | Published September 23, 2011 - Updated September 22, 2011
Virtualization improves IT resource utilization by treating your company’s physical resources as pools from which virtual resources can be dynamically allocated.
This series starts with a background on hypervisor types and system virtualization, and then describes the features of five hypervisors, their deployment processes, and the management issues you might encounter.
Use this series as a simple starting point for understanding the hypervisor’s role in virtualization in the cloud or explore the individual articles to help you determine which hypervisor is best suited for your cloud needs.
Virtualization involves a shift in thinking from physical to logical, treating IT resources as logical resources rather than separate physical resources. Using virtualization in your environment, you are able to consolidate resources such as processors, storage, and networks into a virtual environment which provides the following benefits:
Virtualization is the creation of flexible substitutes for actual resources — substitutes that have the same functions and external interfaces as their actual counterparts but that differ in attributes such as size, performance, and cost. These substitutes are called virtual resources; their users are typically unaware of the substitution.
Virtualization is commonly applied to physical hardware resources by combining multiple physical resources into shared pools from which users receive virtual resources. With virtualization, you can make one physical resource look like multiple virtual resources.
Furthermore, virtual resources can have functions or features that are not available in their underlying physical resources.
System virtualization creates many virtual systems within a single physical system.
Virtual systems are independent operating environments that use virtual resources. Virtual
systems running on IBM® systems are often referred to as logical partitions or virtual machines. System virtualization is most commonly implemented with hypervisor technology.
Hypervisors are software or firmware components that can virtualize system resources
Now let’s look at the types of hypervisors.
There are two types of hypervisors:
Type 1 hypervisors run directly on the system hardware. Type 2 hypervisors run on a host operating system that provides virtualization services, such as I/O device support and memory management. Figure 2 shows how type 1 and type 2 hypervisors differ.
The hypervisors described in this series are supported by various hardware platforms and in various cloud environments:
All of these hypervisors are supported by IBM hardware.
The individual linked articles describe in detail the features, functionalities, and methods to deploy and manage the virtual systems with corresponding hypervisors.
One of the best ways to determine which hypervisor meets your needs is to compare their performance metrics. These include CPU overhead, amount of maximum host and guest memory, and support for virtual processors.
But metrics alone should not determine your choice. In addition to the capabilities of the hypervisor, you must also verify the guest operating systems that each hypervisor supports.
If you are running heterogeneous systems in your service network, then you must select the hypervisor that has support for the operating systems you currently run. If you run a homogeneous network based on Windows or Linux, then support for a smaller number of guest operating systems might fit your needs.
All hypervisors are not made equal, but they all offer similar features. Understanding the features they have as well as the guest operating systems each supports is an essential aspect of any hardware virtualization hypervisor selection process. Matching this data to your organization’s requirements will be at the core of the decision you make. (To get started with this process, explore the details of each hypervisor.)
The following factors should be examined before choosing a suitable hypervisor.
Virtual systems should meet or exceed the performance of their physical counterparts, at least in relation to the applications within each server. Everything beyond meeting this benchmark is profit.
Ideally, you want each hypervisor to optimize resources on the fly to maximize performance for each virtual machine. The question is how much you might be willing to pay for this optimization. The size or mission-criticality your project generally determines the value of this optimization.
Look for support for hardware-assisted memory virtualization. Memory overcommit and large page table support in the VM guest and hypervisor are preferred features; memory page sharing is an optional bonus feature you might want to consider.
Each major vendor has its own high availability solution and the way each achieves it may be wildly different, ranging from very complex to minimalist approaches. Understanding both the disaster prevention and disaster recovery methods for each system is critical. You should never bring any virtual machine online without fully knowing the protection and recovery mechanisms in place.
Live migration is extremely important for users; along with support for live migration across different platforms and the capability to simultaneously live migrate two or more VMs, you need to carefully consider what the individual hypervisor offers in this area.
In networking, hypervisors should support network interface cards (NICs) teaming and load balancing, Unicast isolation, and support for the standard (802.1Q) virtual local area network (VLAN) trunking.
Each hypervisor should also support iSCSI- and Fibre Channel-networked storage and enterprise data protection software support with some preferences for tools and APIs, Fibre Channel over Ethernet (FCoE), and virtual disk multi-hypervisor compatibility.
Look for such management features as Simple Network Management Protocol (SNMP) trap capabilities, integration with other management software, and fault tolerance of the management server — these features are invaluable to a hypervisor.
Now I don’t want to influence your choice of hypervisor (after all, your needs and
requirements are unique), but here are a few general suggestions from my experience with implementation of hypervisors for cloud-based workloads:
You can even try out some of the freeware VMs like Xen and KVM.
IT managers are increasingly looking at virtualization technology to lower IT costs through increased efficiency, flexibility, and responsiveness. As virtualization becomes more pervasive, it is critical that virtualization infrastructure can address the challenges and issues faced by an enterprise datacenter in the most efficient manner.
Any virtualization infrastructure looking for mainstream adoption in data centers should offer the best-of-breed combination of several important enterprise readiness capabilities:
This article introduced the concept of system virtualization and hypervisors, demonstrated
the role a hypervisor plays in system virtualization, and offered some topic areas to
consider when choosing a hypervisor to support your cloud virtualization requirements.
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