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Virtual Servers?

Discussion in 'Tech Talk' started by betyourlife, Nov 11, 2008.

  1. betyourlife

    betyourlife on a GLOCK

    May 10, 2004
    Seattle, WA
    I am trying to figure them out. My understanding is that there are two types, software based and hardware based. Essentially they enable you to use one physical server as virtually several servers. Their uses are? Production and test environments on the same box? Redundancy? Cost when you have a lot of applications?
  2. WhatYouWant

    WhatYouWant Duh!

    Feb 28, 2005
    Land O' Sea
    Yes, one physical server can be sliced into different virtual environments that support different tasks. Do you remember SETI@Home? They want to use your spare cycles to run their search analysis. By using virtual environments you are closer to 100% utilization of your servers. This reduces the number of physical servers required and the associated carrying costs [cooling, electricity, floor space, etc].

    Virtuals can be used to provide: disaster recovery; quick environment provisioning; application sandboxes; etc.

    More Basic Info and links start here.

  3. betyourlife

    betyourlife on a GLOCK

    May 10, 2004
    Seattle, WA
    OK, I don't understand how they would be used for disaster recovery though if it is just software virtualization. It is all still on the same box right? What happens if the box is destroyed, or more likely, the power supply for the box fails? Then what? Let's say you have an application that can't have any downtime. How does a virtual server support this if the physical server the virtual server resides on is down?

    From what I am reading it sounds like with hardware virtualization the resources of the physical server are partitioned so that if one component relative to one virtual server on a box fails, the other one can take over?
    Last edited: Nov 11, 2008
  4. MikeG22

    MikeG22 CLM

    Jun 24, 2002
    San Diego
    You can do a number of things with that. The "server" is then portable once virtualized so say you have two servers and some hardware fails then all you would need would be to moved the virtual server file onto the other box and start it up basically. You can also cluster them in more of a traditional sense so the other can take over processing for both. I just deployed a new VMWare deployment that was really cool. It used a product from Lefthand Networks which takes all the drivespace in 2 servers and makes a virtualized SAN. So you get realtime mirroring of all data between the two boxes so if you did have failure on one physical box you are already set to go to start it up on the other box. You can have nearly zero downtime with the solution if you want to. You can then use other software that provides the high availability to automatically trigger a switchover if you want too.

    In larger virtualized deployments you are accessing the files off of a SAN so the files that you are accessing for the servers to run can be available to as many physical boxes as you want to front-end them.
  5. WhatYouWant

    WhatYouWant Duh!

    Feb 28, 2005
    Land O' Sea
    Depending upon the installation the image file for the virtual environment may not be located on the physical machine (eg: SAN). When the host fails another host can be used to bring the virtual back online. Virtualization does not mean you can go with only one server, it just means you can have less than X physical servers for X applications (minimum of two for us paranoid people).
  6. Also add the following benfits;

    virtual machines( the correct names ) are hosted on a server and can be clone and replicated. Easier to manage, speed up development and testing for testing and roll out.

    Various technologies exists today with VMWare, Sun's Containers , Virtual Box and even Microsoft,etc....
  7. Sgt. Schultz

    Sgt. Schultz Annoying Member

    I use M$ Virtual PC 2007 all the time. I using one right now, it’s probably the safest way to access the Internet, once I’m finished I simply shut it down without saving any changes … that way I get a clean system every restart.

    Once you have a VPC setup (any OS) and configured the way you want it, copy it to another folder and keep it as the original. Using the original as a template you can create as many VPC’s as needed, one for web browsing, one to test your software on different OS versions before roll out, for training computers (it’s faster the disc imaging software) etc ...

    It should be noted that legally you are required to have a software license for each guest (virtual) operating systems.
  8. I've question that and I think most EULA will allow you to "clone" your OS as long as you don't run it simultaneously.

    Think about it, cloning a OS is no different than backing up the OS to tape/disk? Right ?

    But what you can do, I have a virgin XP, windows2003 server that i copy up to my VMs ESXi server or run on fusion, I run it and use it. If I load a bunch of junk on it and it starts to give me problems, than I delete it and clone another VM to use.

    The original never get changes or heavily modified.
  9. Sgt. Schultz

    Sgt. Schultz Annoying Member

    Just to clarify my previous post … with very few exceptions virtual machines are treated exactly the same as physical machines when it comes to licensing. This applies both to the operating system and to applications. Virtual machines are considered separate machines for this purpose; therefore you will need a separate license for the host computer and each of the virtual machines you are running.

    Right, you are allowed to create an image, however there is a difference between cloning a drive and creating a virtual machine. When you clone a drive you create an image that unlike a virtual drive you can’t run at the same time as the original.

    You are also allowed to setup a virtual machine and then create a copy to store as an original and as long as you do not run them at the same time you are good to go …
  10. betyourlife

    betyourlife on a GLOCK

    May 10, 2004
    Seattle, WA
    So what you are saying is that the image could reside completely off the machine in the SAN and another host, such as another virtual server at a completely different location could bring it online if the original host died? That makes sense actually.

    Yeah, I realize that you still need more than one server, just that you need less of them with virtual servers. Being that they are expensive thanks to the licensing I guess you gotta make sure that you use them fully to get your moneys worth. 5K for a server VS 35K for a VM that you are barely using any more than a regular server.
  11. betyourlife

    betyourlife on a GLOCK

    May 10, 2004
    Seattle, WA
    Sounds like clustering them is the best way to avoid ANY downtime? Otherwise it sounds like all the other methods will involve a start up which gives you a couple minutes of downtime.
  12. stooxie

    stooxie NRA Life Member

    Apr 10, 2005
    Northern Virginia
    That's correct. Unless you have a perfectly stateless application architecture (i.e. a bank of static HTML servers) some kind of clustering solution is required for service availability. A virtualization layer can help avoid the loss of a service, but if the service fails due to underlying hardware you would still rely on cluster technologies to protect you.

    One way virtualization can help avoid service loss is by recognizing when hardware failures are imminent (i.e. too many ECC memory errors or failed power supply) and migrating the VMs to another machine.

  13. pmcjury


    Nov 4, 2008
    VMs are great. The biggest advantage in my opinion is smaller foot print on the datacenter floor, less power usage, which means less cooling requirments. And as far as lisencing goes, it verys from vendor to vendor, a lot of software is licensed on a per cpu basis. In that case you can load the software as many times as you want into various VMs and not need any more licenses then running a single OS on the physical hardware. Plus they are great for test environments. you can run lots of VMs on a single physical box (assuming enough horse power and RAM) and have them all networked without ever having to run a single piece of cat6. VMs definatly are not for everyone, but if the fit your needs they are amazing.
  14. DoubleWide


    Sep 3, 2008
    Assuming a powerful server, you can pretty much change what each server gets at will.

    Say two departments want to test out new applications. Throw them on two virtual servers. They underestimated how much cpu, ram, and storage they need. Change the settings. You need Win200, Vista, Linux, done.
    Just remember you're still limited by actual hardware though, but sometimes you don't need that power at the same time. Batch jobs run at night on one server and users need a different server during the day.

    Reducing footprint - replacing many old servers with one new server
    Less electricity and less cooling
    fewer hardware maintenance contracts
    adjustable configurations
    possible ease of administration

    Of course, one problem can affect many, many servers also. Work had a SAN problem one time and every single VM kept rebooting. :steamed: