[OSM-talk] OSM server on a (Ubuntu) VM?

john whelan jwhelan0112 at gmail.com
Wed Dec 22 00:27:15 GMT 2010


On small databases where performance isn't that critical they will work
under virtual machines but larger databases are different.

I was responsible for running large central database servers at Statistics
Canada and we had a server support area who thought Virtual Machines were
the only way to go.

Memory is measured in nanoseconds, disk speeds in milliseconds.  10,000 nano
seconds equals one millisecond.  Basically we got our performance by
switching to 64 bit operating systems and dumping in lots of memory to
primarily avoid dis accesses.  I think we consolidated some 20 database
servers on the one machine with a single cpu with multiple cores.

By contrast those databases that were set up by the server group were often
limited to 2 gigs of memory by the Virtual Machine environment and the
virtual cpus were in fact a maximum of a single core.  This has major
licensing implications if you are running commercial database software.  If
you are running Oracle for example, unless things have changed, you need to
license every cpu on the physical server not just the virtual machine.  They
also had performance issues in part because the virtual machine emulated a
particular older server.  Fine except our servers had later hardware on the
disk side which the database and operating system could take advantage of.
Under emulation they couldn't take the same advantage of the hardware.

Cheerio John

On 21 December 2010 18:47, David Murn <davey at incanberra.com.au> wrote:

> On Tue, 2010-12-21 at 14:31 +0000, Nick Whitelegg wrote:
>
> > Bear in mind though that many of us have to make do with VMs, for
> > financial reasons.
>
> Not entirely sure what you mean by 'for financial reasons', but I agree
> in part.  I do wonder though, if youre using a windows host simply for
> financial book-keeping and a ubuntu database server as a guest, youve
> got things the wrong way around.  Make your host ubuntu and windows your
> VM.  This gets around the performance problems of running a database in
> a VM, and you will infact notice an inprovement with windows running in
> guest mode instead of host mode, as it will benefit from the caching
> available in ubuntu.  Especially if the only reason you need non-ubuntu
> software is for financials, then youre better off having that running
> part-time in a VM and having your main system operation running as host.
>
> Unless you want to simply render once, dont care how long it takes to
> setup or complete, and then delete the whole renderer.  If you expect to
> be using the setup more than once, a virtual machine is not the best way
> to go.. its not even 2nd best.
>
> David
>
>
> >  While trying to load the whole planet or even the
> >  whole of a country like the UK might be difficult, if you try and cut
> >  down the data, then it should (IMX) work reasonably well. For example,
> >  don't try to do the whole world or even the whole of your country, use
> >  a subset of data such as your region, or, if possible try and design
> >  your app to minimise the amount of data it needs (e.g. use osmosis to
> >  cut out irrelevant data).
> >
> > Nick
> >
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>
>
>
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