Server Virtualization

[john_sm3853]

Hey Folks - We need your help. We were hoping, we could gain from your experience with implementing server virtualization. When should we be using Red Hat Virtualization, Citrix Virtualization, Xen Virtualization, Microsoft Virtualization, Oracle Virtualization and VMWare. I will be very interested in learning from your first hand experince. I will also like to know, under what situations is one virtualization prefered over the other. - Thanks for your help

[Steven E. Protter]

Shalom,

I have used the following:
vmware
xen

vmware can be costly but it definitely supports a lot of OS' and such.

xen has limitations as far as supporting windows guests and things like that but its less costly.

We've used windows based server virtualization to support linux guests. We found windows consumes too much resources to present heavy use servers.

The experience is good overall. We have many more servers than two years ago customized for special tasks. Still, for really big applications with hundreds of users we need non-virtual servers.

SEP

[palaniappan.sp]

Hi,
Nowadays ever organisation needs to save cost and at the same time they need a flexibility.hence normally they are going for Server Virtuallisation.
Advanatges of vitualisation:
1) Single HW enough (physical server).
2) But many logical server can be build in one physical server.
3) Suitable for making R&D on the app sw...etc..

Disadvantages:
1) If one OS get crashed or HDD crashed,it is possible for loosing all the datas (quite risky).

In linux RHEL5(licensed) and CentOS5(opensource) comming defaulty with server virtualisation sw.
When u compare unbuntu with the above two OS, unbuntu is a very very light OS.but it is supporting host virtualisation also.

Regds
Palani

[Ivan Ferreira]

Microsoft Virtualization - I won't use it.

Xen Virtualization ~= Red Hat Virtualization: This virtualization is really good as the operating system provides near real physical server performance. Use it when you want to virtualize Linux.

VMWare: Excelent for virtualizing Windows Operating Systems. I had problems virtualizing Linux. Anyway, if you want to virtualize Linux use Xen/Red Hat. But you get some performance degradation compared with a real server.

Citrix: Never play with it.

[Heironimus]

The virtualization in RHEL5 is based on Xen, though I've heard that in the future Red Hat's virtualization will be based on KVM instead. Oracle VM is also based on Xen, I assume with some optimizations for Oracle databases, but it's still very new. Citrix recently acquired XenSource (the Xen company), so their upcoming virtualization products will probably also be Xen.

[Stuart Browne]

In my mind, it depends on the scale of virtualization needed.

If you're just wanting to set up some test servers, then using either VMWare Server, or any of the xen based products is fine. It allows a host OS to completely own it's self, and any guest OS' you set up, usually on a virtual disk, but physical disks (or SAN) dedicated to a VM work fine as well.

If you wan't something bigger, then as far as I'm aware, VMWare (ESX, part of Inferstructure) is your only choice.

Where as VMWare Server, Xen, the Citrix solutions (Xensource) are all based on virtualisation within an existing operating system, and more importantly within a given physical system, ESX allows you to scale a virtual machine across multiple physical machines.

The Hypervisor in ESX *IS* the OS, so the OS overhead is already minimal.

This means less abstraction, which means fewer speed degredation issues.

The Hypervisor of Xen is built into the kernel (of which ever OS you use as your base, usually Linux in this community, but other solutions exist).

I personally use Xen at home. I've tried both Centos5 and Fedora 8's releases, and haven't had any major issues with running either Windows XP or numerous Linux distributions. I've not tried any of the Server windows distributions however.

At work, I've used VMWare Workstation a fair amount (used to run 7 virtual machines on my poor desktop *sob*sob*. Memory exhaustion!), also didn't have any issues there.

In terms of stability however, you've got both the Guest OS's stability to be concerned about, as well as the Host's stability. I'm yet to have a Guest who was less stable than it's Host however.

So as I said, it all comes down to a question of scale.

[Emil Velez]

Why not consider the virtualization of the 64 bit IA-64 architecture where the VMs can be VMS, Windows 64 bit, Linux 64 bit, and HPUX.

Itanium Virtual machine

[Andrew Cowan]

John,

I would tend to start testing with VMWare Server 1.X on Windows and Linux, as these are free products and can be easily installed and removed without causing any problems for the host machines.

VMWare 2.x beta is available, however it is fairly unstable at the moment, and these problems might confuse you.

Remember that whatever product you choose, that the host needs to be as powerful as possible, with lots of spare memory and disk space, and if possible, newer processors that support native hyperthreading, multiple pipelining, etc.

If you install Windows, don't activate each copy, instead take snaphots and keep restoring before the 3o days is up. This is perfectly legal as far as Microsoft is concerned, so long as it is only for testing. This will also apply to products such as Office.

Both Microsoft Virtual-PC and VMWare provide downloadable prebuilt and configured virtual machines, that in many cases can be imported or converted to work with other virtualisation products.

My personal findings are:
Of all the products I've tested, I like VMWare Server the best.
VMWare is far more efficient when run under Linux, however this should be balanced against the slightly harder install and maintenance overheads.
My experience with XEN is limited, however it seems much fussier than VMWare, and less stable.
VMWare 2.x looks as though it could be good in time, however the current version is very slow and unstable, and NOT for the faint-hearted.
VMWare also benefits from the large number of discussion groups available.