You probably know a little about virtualization if you have ever divided your hard drive into different partitions. A partition is the logical division of a hard disk drive to create, in effect, two separate hard drives.
Operating system virtualization is the use of software to allow a piece of hardware to run multiple operating system images at the same time. The technology got its start on mainframes decades ago, allowing administrators to avoid wasting expensive processing power.
In 2005, virtualization software was adopted faster than anyone imagined, including the experts. There are three areas of IT where virtualization is making headroads, network virtualization , storage virtualization and server virtualization .
- Network virtualization is a method of combining the available resources in a network by splitting up the available bandwidth into channels, each of which is independent from the others, and each of which can be assigned (or reassigned) to a particular server or device in real time. The idea is that virtualization disguises the true complexity of the network by separating it into manageable parts, much like your partitioned hard drive makes it easier to manage your files.
- Storage virtualization is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console. Storage virtualization is commonly used in storage area networks (SANs).
- Server virtualization is the masking of server resources (including the number and identity of individual physical servers, processors, and operating systems) from server users. The intention is to spare the user from having to understand and manage complicated details of server resources while increasing resource sharing and utilization and maintaining the capacity to expand later.
Virtualization can be viewed as part of an overall trend in enterprise IT that includesautonomic computing, a scenario in which the IT environment will be able to manage itself based on perceived activity, and utility computing, in which computer processing power is seen as a utility that clients can pay for only as needed. The usual goal of virtualization is to centralize administrative tasks while improving scalability and work loads.
How to Virtualize
The primary action in setting up a virtual server is selecting and installing the virtualization layer. Here are some of the more popular options.
- Xen 3.0:
Xen is a lightweight open source hypervisor (less than 50,000 lines of code) which runs on Intel or AMD x86 and 64-bit processors, with or without virtualization technologies. It supports up to 32-way SMP (Simultaneous Multi Processing) and requires a modification of the client operating system, which means it will run Linux but not Windows clients. Although the original Xen hypervisor works only with Linux clients, XenSource, the company behind the Xen project, released XenEnterprise, a version that supports Windows Server and Solaris guests as well.
- Windows Virtual Server 2005 R2:
Microsoft initially charged for its virtualization technology, and it was limited to Windows servers. With Windows Server 2003R2, customers can run up to four operating systems on a physical server. On April 3, Microsoft announced it was making Virtual Server a free download, and it extended support to clients running nine versions of Red Hat and SUSE Linux.
- VMware Server:
VMware (EMC) is by far the largest vendor of virtualization technology for x86 platforms. In early 2006, the company released VMware Server, a replacement for GSX Server, which is a single server virtualization platform for Linux and Windows. More than 100,000 downloads of this free product were made in the first week alone. VMware Server has all the features of the GSX Server, and adds support for virtual SMP, Intel Virtualization Technology and 64-bit guest operating systems.
- VMware ESX Server:
Although its entry-level product is now free, VMware still charges for its enterprise-class ESX Server. ESX server runs on x86-based servers and supports Linux (Red Hat and SUSE), Windows (Server and XP), Novell NetWare and FreeBSD 4.9 clients.
- Virtual Iron:
Virtual Iron is another company offering Xen-based products. It has four products: two free single server versions, an enterprise version and one for clusters. In addition to the Xen hypervisor, Virtual Iron also includes management tools and an administrative interface.
- IBM Virtualization Engine Platform:
This platform encompasses the entire line of IBM servers. As well as the usual hypervisor for server partitioning, it includes virtual I/O and virtual Ethernet, a workload manager and management console.