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Thin Client and Virtual Machines Thread, Virtualization in Technical; No problem about the cost - just need a few solutions....
  1. #16

    Hightower's Avatar
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    No problem about the cost - just need a few solutions.

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    tmcd35's Avatar
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    Linux.com :: Live migration of Xen domains

    Xen is the cheaper alternative. And will do the job. Both Xen and vMWare require a 'common data source' or basically a shard hard drive that all three physical machines have access to. vMWare will do this from a NFS share, but ideally a SAN is required for either solution. It's not worth is unless we are talking running atleast 10 OS's across the 3 servers.

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    How about running a 4th older server with plenty of storage as the common data source? Will this do?

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    Quote Originally Posted by tmcd35 View Post
    Xen is the cheaper alternative. And will do the job. Both Xen and vMWare require a 'common data source' or basically a shard hard drive that all three physical machines have access to. vMWare will do this from a NFS share, but ideally a SAN is required for either solution. It's not worth is unless we are talking running atleast 10 OS's across the 3 servers.
    This has been our strategy. Xen is free and will do what we want. Spend the money on SAN, fibre cards and VT capable servers.

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    Quote Originally Posted by Hightower View Post
    How about running a 4th older server with plenty of storage as the common data source? Will this do?
    not if you want any sensible performance. you could set it up as an iscsi target though.

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    Do you already run a system similar to this CyberNerd? If so, what is your set up?

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    I used to do this where I worked before in industry. We had a VAX cluster running OpenVMS for our manufacturing and financial system. What you might want to consider is that although the OS will continue to work fine if you down one of the servers for maintenance, you have to remember that any hardware resource within or directly attached to that server will no longer be available. So on a basic level the hard drive in the downed server will no longer be available and therefore none of the data etc... stored on it.

    We used a stand alone disk array for data storage which meant that if one of the servers failed etc... the other server could continue without any problems and the users would be unaware of any change as all data was still there.

    The costs as mentioned above are higher as well as making setup and maintenance that bit more complex.

    Richard

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    Quote Originally Posted by Hightower View Post
    Do you already run a system similar to this CyberNerd? If so, what is your set up?
    it's not setup. We have an 18month strategy, this summer we put in a SAN. now I'm playing the clustering and XEN

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    What are you using (which OS) to run Xen on? I'm having a look at opensuse now.

    Think the best thing I can do it get three similar spec'd machines and try it, using 2 as the VM servers and one as the central storage.

    This thing is giving me a headache but I'm loving it as well - it's making my brain work hehe.

    On a sub-topic, anyone know of any virtualization courses I can go on?

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    Quote Originally Posted by Hightower View Post
    Lets say we have 3 physical servers. And we want 2 independant OS's. How do I get both the OS's to work independantly across all 3 servers? Yes, as a way of load balancing but also for redundancy ie we might want to take the 3rd server down for maintenance but nothing is affected as the OS's are still working perfectly across the 2 remaining servers (albeit a bit slower).
    You don't run an unmodified OS across two physical machines, the communications overhead is too much. You need an OS on each machine that supports clustering (various variants of Windows / Linux / etc) and application support for clustering too. I think instead you're maybe thinking of "cloud" computing, where you have a bunch of virtual machines that can be moved around your pool of physical machines at will. I've set our machines up using Xen, which proved to be dead easy with CentOS (like, select "virtualisation" and "clustering" from the install menu, done). I do auto fail-over with DRBD, mirroring whole Linux block devices on physically separate machines, but I know other people prefer to use a SAN (but I figure the SAN is just as likely to fail as one of the processing machines...).

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    Quote Originally Posted by dhicks View Post
    I think instead you're maybe thinking of "cloud" computing,
    Nope, I know each physical machine needs an OS. And then on that OS it has a VM.

    Any what I want to do is share that VM with the other 2 machines so they're all chipping in.

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    Quote Originally Posted by Hightower View Post
    What are you using (which OS) to run Xen on?
    I've found CentOS to be very easy to use.

    Think the best thing I can do it get three similar spec'd machines and try it, using 2 as the VM servers and one as the central storage.
    For performance, I figure it's best to have storage local to the processor running each VM, unless you have a decent SAN to hand. I mirror whole volumes between machines with DRBD. Okay, this means you spend more on harddrives, but I still figure that's less these days than fancy SAN networking equipment.

    On a sub-topic, anyone know of any virtualization courses I can go on?
    Didn't manage to convince the bursar that VM World in Las Vegas was a vital training opportunity...

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    Quote Originally Posted by Hightower View Post
    Any what I want to do is share that VM with the other 2 machines so they're all chipping in.
    All three machines are contributing to the processing of that (general-purpose) VM, you mean? As in you want to stick three PCs together with Ethernet cable, do some clustering magic and run Windows as a VM on top of your new "three processor" machine? As far as I know, this isn't possible. The communications bandwidth and latency available between your machines is the limiting factor - that's why processors and RAM are very tightly coupled. Admittedly, there are probably ways to get around this, but it would involve a specialist OS and application software written with clustering in mind, and maybe a different instruction set than 80x86 (i.e. the kind of thing the Transputer was designed to be).

    Is the above an accurate description of what you're trying to accomplish? What task do you want to get your super-computer cluster to do? If it's to do something like serve web pages then you have one machine act as a load balancer, controlling which of the other machines gets to process each incoming HTTP request.

    If you want a fun/cheap way to practice at this, without having to buy a stack of hardware, then Amazon EC3 (and similar services) is worth a look. If you're just trying to write a bit of software to run in a distributed manner then maybe Google Python-based service is what you need.

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  14. #29

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    As I read this your talking about 2 OS's across 3 hardware platforms with even load spreading across it rather than 2 live environments and an idle backup.

    If that is the case then your going the wrong way at this. Yes it can be done but its expensive VERY VERY expensive and I can see no real world scenario outside of the Eve online server where this is necessary or even desirable.

    As posted above the bandwidth requirement to share tasks at a process level is just too intensive your talking infiniband technology with a custom written or heavily customised OS to make it work and even then unless your doing very compute heavy tasks on it its never going to pay back the investment.

    If redundancy a transparent failover is your goal then you want to VM your Individual servers in a standard Windows environment config ie. DC1, DC2, Print server, Fileserver, Exchange, Web, SIMS. You buy 2-4 powerful multiprocessor servers or a bladeserver pick a virtualisation environment such as hypervisor VMware or Xen and run your 7 virtual servers on that hardware from shared fault tolerant storage and in the event any of your physical servers crashes your users will because the VM management software will start the VMs that were running on the failed server on one of the healthy servers increasing load on them possibly leading to some slowdown for users but no loss of service.

    You could also cluster critical services using windows clustering technology across your Virtual servers so that in the event of one of them failing your services are also unafected.

    If you really need the raw processing power of multiple machines then your better staying away from virtualisation altogether. Even with the hardware support maturing as soon as you bring the word virtual into it you are not making the most efficient possible use of your hardware. You should look into compute clusters and render farm technology. Many of the universities have papers detailing the development of they're computation farms. From design documents for purposebuilt systems from IBM or for in house efforts built from off the shelf hardware such as beowulf clusters.

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