vmware

Understand the differences between VMware's Workstation, GSX, and ESX

VMware GSX Server

VMware Workstation supports only one CPU and up to 1 GB of RAM. GSX Server supports 2 CPUs and up to 2 GB of RAM. GSX Server is very similar to Workstation in most other ways, but one of its coolest features is the Remote Console that allows you to remotely manage and access your virtual machine from anywhere on your network. In addition, it's much easier to work with in a high availability configuration.

While VMware Workstation is mostly used by a single user to run multiple instances of operating systems for testing and support purposes, GSX Server is often used for server consolidation by running virtual machines of server operating systems that simply appear to be stand-alone servers to clients on the network.

VMware ESX Server is mainframe-class virtual machine software. This solution is typically used by mainframe data centers and cutting-edge companies. I've also seen this solution used by startup companies. With ESX Server, you can do amazing things such as more extensive server consolidation and virtual machine clustering.

How does it differ from GSX Server and VMware Workstation?
With VMware Workstation and GSX Server, the software sits on top of a host operating system such as Windows or Linux. With ESX Server, the software runs directly on the system's hardware, eliminating the need to install a base OS. In fact, ESX has its own OS. The software basically runs on its own Linux kernel, and Linux is quite beneficial to know when working with the product, although it's not an absolute necessity.

Installation of this product is quite basic. You place the CD in the tray of a system and boot from the CD. It runs you through a typical Linux installation. At the end of the install, you're instructed to go to a separate machine and type in a specific Web address to access the virtual console of ESX Server. From there, you'll configure your system and create virtual machines. With ESX Server, you can have up to 3.6 GB of RAM per virtual machine as well as high performance network cards.

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Performances versus flexibility

Apart price, the very first difference between VMware Server and ESX Server every consultant or salesman would underline is performance achievement.

At today nobody ever published a benchmark comparison between the two platforms running the same virtual machine on the same hardware, but they way they are architected let people presume which products performs better.

While VMware Server needs an underlying operating system to be installed on, its bigger brother ESX doesn't: it's a bare metal solution as the industry usually calls it.

In other words part of ESX Server acts as an operating system, booting the hardware and managing it to achieve all required virtualization tasks, in the same way an appliance would do.

This difference in approach reflects a deep difference in behaviour: while Server capabilities and performances are capped by the hosting operating system, ESX Server is designed to take out the most from available hardware, with the thinnest OS layer possible.

Performing by design means ESX Server can offer customers not only better performances, but also a better consolidation ratio: the amount of concurrent running virtual machines which can be safely allocated for each CPU core in the physical host.

While VMware suggests keeping this ratio between 2 and 4 with Server, customers can reach 4 to 8 with ESX.

These values are highly dependant on expected workload on running virtual machines and on hosted applications inside: a very busy ESX Server may not allow more than three virtual machines per core while a very light Sever could easily run 10 web servers per core.

But in general they can be considered as a good reference point.

The ESX Server capability to directly control hardware components permits to improve performances also in other aspects: for example VMware developed a special file system called VMFS where to store virtual machines, which is faster and more reliable than traditional multi-purpose file systems modern operating systems offer.

Unfortunately when a virtual machine stored on VMFS needs to be migrated on another VMware product its format has to be converted.

VMware Server cannot count on VMFS and its performances depend on Windows and Linux file systems but its virtual machines can be moved on the fly on any computer with a burned DVD or a USB key, considering it just like a standard folder with a bunch of files.

But a bare metal approach brings severe limitations along with benefits: since the product itself acts as an OS, only hardware which has its drivers included will work.

So, for example, at the moment of writing VMware doesn't include drivers for local SATA disks in ESX Server, and customers adopting it have to choose between local SCSI disks or remote storage facilities, like NAS and SANs.

Customers must also be aware that not only single equipment pieces could not be usable, but a whole machine could not as well: VMware reserves itself right to officially support only a limited amount of systems on the market, so we cannot run ESX Server on any hardware available in our datacenter and receive support for it.

The hosted approach of VMware Server instead permits to rely on underlying operating system for hardware support and drivers availability.

Anything the OS can do, like connecting a remote iSCSI disk or driving a local tape backup unit, is immediately available for Server virtual machines use.

Software availability and support is impacted as well by this difference in approach.

In ESX Server there is a limited amount of installed service utility, new installed applications could not work on it because some mandatory libraries are missing, and customers are highly discouraged to add them, to not mine reliability of the whole system.

This reduces risks but can translate in administrative pains anytime VMware didn't implement a component needful for us.

In VMware Server environments any program can be installed on the host operating system, allowing customers to achieve tasks like disks defragmentation or backup, performance monitoring or remote management, with tools of their choice, maybe returning on an investment already done before.

ESX Server is much more integrated with VirtualCenter than Server, and can perform more complex operations like the famous VMotion: migration of a virtual machine from a physical host to another without interruption of service.

Another impressive capability permits to dynamically move away a running virtual machine from the physical host where it's running if it becomes overloaded, and to place it on a less busy server. All without manual intervention and without interruption of service.






Reference:
http://www.virtualization.info/2006/12/choosing-between-vmware-server-and-esx.html
http://articles.techrepublic.com.com/5100-6350_11-5109611.html