SVISTA

SVISTA (Serenity Virtual Station) is one of the commercial software products promoted by Serenity Systems International. The workstation software consists of a virtual machine suite for Intel x86-compatible computers which allows the creation and execution of multiple x86 virtual computers simultaneously. Each virtual machine instance can execute its own guest operating system including Windows, Linux, OS/2 and BSD variants. In simple terms, SVISTA allows one physical machine to run numerous operating systems simultaneously.

Description

The computer and operating system instance that executes the SVISTA process is referred to as the "host machine". Instances of operating systems running inside a virtual machine are referred to as "guest virtual machines". Like an emulator, SVISTA provides a completely virtualized set of hardware to the guest operating system; for example, irrespective of make and model of the physical network adapter, the guest machine will see an Novell/Eagle NE2000 or Realtek RTL8029(AS) network adapter. SVISTA virtualizes all devices within the virtual environment, including the video adapter, network adapter, and hard disk adapters. It also provides pass-through drivers for serial and parallel devices.

Because all guest virtual machines use the same hardware drivers irrespective of the actual hardware on the host computer, virtual machine instances are highly portable between computers. For example, a running virtual machine can be stopped, copied to another physical computer, and started.

Implementation

Conventional emulators like Bochs emulate the microprocessor, executing each guest CPU instruction by calling a software subroutine on the host machine that simulates the function of that CPU instruction. This level of abstraction allows the guest machine to run on host machines with a different type of microprocessor, but is also very slow.

A more efficient approach consists in software debugger technique. Some parts of the code are executed natively on the real processor; on 'bad' instructions, there are software interrupts that break execution of the guest operating system code and that particular instruction is emulated.

SVISTA, as well as VMware Workstation, Virtual PC for Windows and QEMU with the kqemu add-on, take an even more optimized approach and run code directly when this is possible. This is the case for user mode and virtual 8086 mode code on x86.

The drawback is that the guest OS has to be compatible with the host CPU. So unlike an emulator, one cannot use SVISTA to run Mac/PowerPC software on an Intel x86 processor. Another drawback is that it is not normally possible to efficiently nest SVISTA virtual machines. Finally, although SVISTA virtual machines run in user mode, SVISTA itself requires installing various drivers in the host operating system.

Features

Besides bridging to network adapters, CD-ROM readers and hard disk drives, SVISTA also provides the ability to simulate some hardware. For example, an ISO image can be mounted as a CDROM and .hdd files can be mounted as hard disks.

Issues

When using SVISTA instances in an environment where MAC addresses are used as unique identifiers (UID), it is advisable to manually configure the MAC address for each virtual machine to ensure each is actually unique. One example of such an environment is one in which MAC security is enabled on switches and another example is an environment in which Altiris products are used (if configured to use the MAC address as the UID). If you are in such a situation, simply disable all networks/adapters other than bridged and edit each virtual machine's configuration (.2os) file and change the 'MAC address' to be unique.

ee also

* VMware
* Parallels Workstation
* User Mode Linux
* Xen (virtual machine monitor)
* Comparison of virtual machines

External links

* [http://www.serenityvirtual.com/ Serenity Systems International]