Difference between revisions of "Creating VMware Server 2.0 Virtual Machines"

Revision as of 18:51, 30 September 2008

So far this book has focused on installing VMware Server 2.0 and gaining familiarity with the VI Web Access interface. The purpose of VMware Server is, of course, the creation of one or more virtual machines running guest operating systems. The VI Web Access management interface makes this task easy through the use of a wizard interface which guides the administrator though the step by step process of configuring and creating new virtual machines.

Accessing the Create Virtual Machine Wizard

The Create Virtual Machine wizard is launched from within the VMware Infrastructure Web Access interface (for more information on accessing and logging into VI Web Access read the chapter entitled A Guided Tour of the VMware Server 2.0 Infrastructure Web Access Interface).

Once logged into the VI Web Access interface, the New Virtual Machine wizard may be invoked in a number of different ways:

• From the Virtual Machine menu option select Create Virtual Machine

• With the host selected in the Inventory panel, click on the Create Virtual Machine link in the Commands section of the Summary or Virtual Machine page of the workspace.

Creating a New Virtual Machine

When loaded, the Name and Location screen of the wizard will appear as follows:

On this screen, the virtual machine should be given a suitably descriptive name such that it will be easily distinguished from other virtual machines running on the host. In addition, the datastore of the virtual machine (where files such as the virtual disk images will be stroed) also needs to be specified. By default a single datastore will have been specified during the VMware Server installation process. To add additional datastores simply click on the Add Datastore link in the Command section of the host Summary workspace and configure the desired storage location.

Once the virtual machine has been named and assigned a datastore, click next to configure the guest operating system type as illustrated in the following figure:

The guest operating system is selected by family and version. For example, once Windows operating system has been selected, the specific version must then be selected from the drop-down list. It is important to note that even if a guest operating system is not listed, it does not necessarily mean it will not run within VMware Server 2.0. In fact, it is usually sufficient to select the closest match from the list. In the case of unsupported Linux distributions, identify the kernel version (current versions are 2.4 and 2.6) and whether the operating system is 32-bit or 64-bit, and then make an appropriate selection from the Other Linux options. For a complete list of officially supported guest operating systems, refer to the Officially Supported VMware Server 2.0 Guest Operating Systems chapter.

Product compatibility is another issue which needs to be considered during the virtual machine creation process. VMware has, over the years, provided a number of different versions of virtual machine hardware VMWare Server 2.0 uses version 7 by default for virtual machines, which provides new features such as 8Gb of memory and up to 10 network adapters per virtual machine. One disadvantage, however, of using version 7 of the virtual machine hardware is that it will not be possible to migrate these virtual machines to VMware environments which use older versions of the virtual machine hardware. For example, a VMware Server 2.0 virtual machine running on virtual machine hardware version 7 will not be able to migrate to a host running VMware Server 1.0 or, for that matter, the current release of most other VMware products. If compatibility is of grater priority than the features offered by virtual machine hardware version 7, then it is best to select version 4 on this screen of the wizard.

Virtual Machine Memory and CPU Settings

Once the name of the virtual machine, and type of guest operating system have been defined, the next screen allows the CPU and memory settings for the virtual machine. It is on this screen that the virtual machine's share of the physical resources of the host computer are defined. The values specified here will dependent on a number of factors. Firstly, the settings will to a large extent be governed by the amount of physical memory and and CPUs available on the host. Secondly, the resource requirements of any other future or currently running virtual machines on the host must also be taken into consideration. In order to assist in arriving at suitable memory settings, the wizard will display recommended, maximum and minimum sizes based on a number of factors including available host resources and the selected guest operating system.

After memory has been assigned to the virtual machine, the number of CPUs or CPU cores to be made available the virtual machine may be configured. Once again, the optimal setting will depend on the CPUs available on the host together with the requirements of both the host operating system and any other virtual machines:

Hard Disk Configuration

Most guest operating systems will require that the virtual machine contain a virtual hard disk on which to store both the operating system itself and applications and user data. In a VMWare Server virtual environment, the hard disks assigned to virtual machines are actually disk image files (with the filename extension .vmdk) that reside on the filesystem of the host much like any other data file. As such, a hard disk can be assigned to a virtual machine either by requesting that a new disk image file be created, or by re-using a disk image file created for another virtual machine (though it is important to ensure that the disk is currently in use by the other guest).

When creating a new disk image for the virtual machine, it is first necessary to define the size of the disk. Any size may be specified up to a maximum of 950GB. The second step is to specify whether the entire disk image should be created now as a single file, or whether the disk should be created at a minimal size, then enlarged as more space is needed. Splitting the disk up has the advantage that not all of the disk space is taken form the host until it is needed and the creation process is faster (creating a large pre-allocated disk can take a considerable amount of time). The downside of using a so called growable disk is that write operations may be slower at the point that the disk needs to be enlarged. In addition, it is also possible to have the disk created as multiple 2GB files instead of as one large contiguous data file. This can be useful on older operating systems where file sizes greater than 2GB are not supported.

In addition, the more advance Disk Mode setting needs to be configured. If the disk is defined as independent then the disk is excluded from any virtual machine snapshots. Independent disks can be either persistent, where any data written to the disk by the guest operating system is retained when the system is powered off, or non-persistent where any data written to the disk by the guest operating system is discarded when the virtual machine is powered off.

The virtual device node settings allow the disk type to appear to the guest operating system as either an IDE or SCSI disk drive. A recommended default selection is provided based on the guest operating system selected at the start of the wizard, although this may be changed if required.

Finally, the disk write caching policy needs to be defined which essentially defines the point at which new data is written to the virtual disk (as opposed to being cached in memory before being written) by the guest operating system. A choice of two options are available:

• Optimize for safety - Data is not cached. Write operations made by the guest operating system are written immediately to the virtual disk image. Reduces risk of data loss in the event of a system failure, but results in slower disk write performance.

• Optimize for performance - Write operations performed by the guest operating system are initially cached prior to being written to the virtual disk. Provides increased write performance at the cost of increased risk of data loss on system failure.

Configuring Virtual Machine Networking

If networking is a requirement for the virtual machine, click on the Add a network adaptor link on the Network Adapter page of the wizard to invoke the Network Adapter properties page. The first option defines the type of network connection to be used by the virtual machine. The options available will depend on the settings chosen during VMware Server 2.0 configuration and fall into the following categories:

• Bridged networking — Although the guest systems use the physical network connections on the host system, each guest is treated as an independent client on the network. As such it will obtain an IP address from the network's DHCP server, or will require a static IP address to be manually configured if DHCP is not used. Guest systems using bridged networking will be able to communicate directly with both the host and other clients on the network to which the host is connected.

• Network address translation (NAT) — Virtual guests share the IP and MAC address of the host system. Guests will be able to communicate with other clients on the network to which the host is connected, but will appear to those clients as the host system, rather than as individual network clients. This approach allows multiple systems to operating using a single IP address. Internally, the guests have their own IP address, but are actually using the IP address of the host when communicating on the network.

• Host‐only networking - Creates a private sub-net within the host for the guest systems. Guests configured with host-only networking can communicate directly only with the host system and other guests which are also members of the host-only network. The guest systems cannot, however, communicate with the network to which the host is connected.

If the network adapter is not to be automatically activated when the virtual machine is powered on, unset the Connect at Power On toggle, otherwise leave the setting at its default value of Yes.

Configuring a CD/DVD Drive or ISO Image