Re: 64 bit linux on VM to run Java app

Discussion in 'Java' started by, Jun 19, 2008.

  1. Guest

    On Jun 19, 10:35 am, General Schvantzkopf <>
    > On Thu, 19 Jun 2008 06:50:55 -0700, wrote:
    > > Can we install a VM to support 6 GB memory on a 32-bit machine?
    > > Basically we want to install 3 VM's running linux sharing the 6 GM
    > > memory. At the first glance it seems not possible. Do we need a 64-bit
    > > processor with 64 bit linux (Red Hat Mandriva, Fedora, etc.). Also since
    > > we will be running Java on the VM's do we need 64-bit Java compiler as
    > > well?

    > > Thanks for your help

    > You need a 64 bit machine to run a 64 bit OS even in a VM. A 32 bit
    > machine can support 6G of RAM but each thread is limited to 3G so it
    > would certainly possible to run three 2G VMs on a 32 bit system. However
    > the 32 bit processors lacked hardware support for VMs so performance of
    > three VMs will suffer. The Core2 Intel and socket AM2 AMD processors have
    > hardware VM support so you should probably get a new system for that
    > alone.
    > Your choice of Virtualizers depends on how your virtual IO requirements
    > and if you need a virtual desktop. The free version of VMware, VMware
    > Server, has no support for shared folders (i.e. the ability to mount a
    > host directory in the VM), so the only way to access the host's file
    > system is through NFS. The performance of NFS on VMware sucks so if you
    > are doing a lot of disk IO to the host you don't want to use VMware
    > Server. If you are doing all of your disk IO to the virtual disk then the
    > performance is quite good and Server works fine. VMware Workstation is
    > nearly identical to VMware Server but with the addition of Shared
    > Folders. Shared Folders fixes the virtual IO problem so if you want to
    > access the host's disks you should used VMware Workstation ($189).
    > Workstation and VMware Server 2.0 (which is still beta) support 8G of
    > RAM, VMware Server 1.0.6 (the production version of Server) only supports
    > 3.6G of RAM. The console performance of the VMware products is excellent
    > so if you need a virtual desktop you will want a VMware product. VMware
    > works with or without hardware support, but faster if you have hardware
    > support.
    > Another option is KVM (Kernel Virtual Machine) which is built into the
    > Linux kernel. You will want a very recent distro for this like Fedora 9.
    > KVM lacks shared folders and it's NFS performance is truly awful, twice
    > as slow as VMware, but it's performance if you are only accessing the
    > virtual disk is almost the same as native. The virtual console on KVM is
    > also awful, it's very nearly unusable. However if you are running a
    > server you don't need a virtual desktop so the bad console performance
    > won't matter. KVM requires hardware support so you will need a Core2 or
    > newer A64/Opteron to use it.
    > I haven't bothered to benchmark VirtualBox for a couple of reasons. The
    > most important is that it's limited to 2G which is inadequate for my
    > purposes. The second is that getting networking to work is really
    > painful. Networking works out of the box on VMware and KVM. VMware is the
    > most flexible, it allows you to have bridged, NAT or host only networking
    > or any combination. You can also easily specify the IPs of the subnets
    > and you can have multiple nets. KVM is NAT out of the box, if you are
    > happy with that it's fine. VirtualBox requires that you create a bridge
    > on the host and do a lot of manual configuration. A VirtualBox VM can
    > access the outside world out of the box, but the external world can't
    > access the VirtualBox VM without doing a lot of hand configuration.
    > VirtualBox does have Shared Folders and it has a very nice GUI and good
    > console performance.
    > Here are some benchmarks that I ran over the last few days. I was running
    > an NCVerilog regression which does a fair about of IO. As you can see as
    > long as you are using a virtual disk the performance is excellent on both
    > VMware and KVM. If access the host disk then only VMware Workstation has
    > good performance.
    > Native                          06:34
    > VM Server 2, virtual disk       08:05
    > VM Server 2, NFS                18:37
    > VM Workstation, shared folder   08:14
    > KVM, Virtual disk               07:42
    > KVM, NFS                        38:36

    Thank you for your kind responses. We want to use Windows as the host
    system. Does it have to be 64-bit? Based on your responses, it seems
    we can run 32-bit OS and 32-bit Java app on the 3 VM's we are going to
    host with 6GB memory.

    Once again thanks a lot for your help.
    , Jun 19, 2008
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  2. Roedy Green Guest

    On Thu, 19 Jun 2008 07:43:48 -0700 (PDT), ""
    <> wrote, quoted or indirectly quoted someone
    who said :

    >Thank you for your kind responses. We want to use Windows as the host
    >system. Does it have to be 64-bit? Based on your responses, it seems
    >we can run 32-bit OS and 32-bit Java app on the 3 VM's we are going to
    >host with 6GB memory.

    Vista does. The catch is the number of device drivers is limited. You
    may find you can't access some of your more exotic peripherals. For
    experimenting, that may be ok. You may have to replace some, e.g.
    your Ethernet card with something supported.

    Roedy Green Canadian Mind Products
    The Java Glossary
    Roedy Green, Jun 20, 2008
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