Matt Miller wrote:
>I am looking for opinions - the pros/cons - on UML and VMWare.
>
>I will be building servers to house multiple Oracle installations to be
>used as development DBs and I wish to run them in self-contained virtual
>environments. Does anyone have experience running Oracle on Linux (on
>Linux) in a virtual environment? Can anyone think of any pros or cons in
>running this in UML or VMWare? Or why they feel one would be better than
>the other?
>
>
Sure. It'll work. It all depends on what type of load you're looking at,
and what kind of footprint you want to have on the host.
Honestly, give both methods a try and decide for yourself. VMWare isn't
free.
>Here is my only criteria -
>
>- The VM environment can run Oracle.
>
>
VMWare, Xen, UML, Colinux, or QEMU can be used to this end. Oracle is a
user mode process that plays well under any of the virtual environments.
The biggest problems you are likely to have are IO contention
(particularly with older versions of UML) and large memory issues
(Oracle can be a RAM hog).
>- I can backup the image (or clone the image for backups) with little
>interruption to the Oracle instances.
>
>
VMWare 4.0 has snapshots. They're actually kind of neat.
There is a User-Mode-Linux "suspend" patch that lets you freeze an
image, back it up, and restore from the suspend to continue.
Xen is working on suspend and restore as well - I believe they have
something in cvs now.
I haven't seen anything in the Colinux park to do this yet - though
there were a few folks who talked about this.
>- Control over memory and CPU utilization between the VM environments and
>the hosts.
>
>
While there are scheduler patches out there that allow you to police CPU
usage of user mode processes, I haven't seen anything that works with
the VMWare CPU virtualizer kernel module (vmmon.o). There has been some
discussion about this on the UML lists, you may want to read through the
list archives there to find some solutions that might help you do this.
If your VM is entirely user-space, you can always nice the processes.
The larger problem is actually policing IO, which the newer cfq stuff in
2.6.5 does really help.
All of the virtual machines methods allow you to allocate memory -
though there are some differences as to how they accomplish this goal.
- Ian
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