Re: Tips for a system with _extremely_ slow IO?

On Fri, Dec 17, 2004 at 11:51:12PM -0800, Ron Mayer wrote:
> Any advice for settings for extremely IO constrained systems?
>
> A demo I've set up for sales seems to be spending much of it's time in
> disk wait states.
>
>
> The particular system I'm working with is:
>    Ext3 on Debian inside Microsoft VirtualPC on NTFS
>    on WindowsXP on laptops of our sales team.
> Somewhat surprisingly, CPU performance is close to native; but disk IO
> is much worse - probably orders of magnitude worse - since there are
> so many layers of filesystems involved.  Unfortunately, no, I don't
> think the sales guys will upgrade to BSD.  :)
>
> The database is too large to fit entirely in memory (3GB of spatial data
> using PostGIS); and has relative large updates (people can add "layers"
> consisting of perhaps 10000 points, lines, and polygons out of a million
> or so possibilities - they do this by doing 10K inserts into tables with
> postgis geometry columns).

I've found VirtualPC to be somewhat slower than VMWare for some things (and
faster for others) and less friendly to a Linux guest OS. Try an identical
build running inside VMWare.

Can you run the VM using a native disk partition, rather than one emulated
by a big NTFS file?

Even if your application needs to run under Linux, can you run the
database directly on XP (8.0RC2 hot off the presses...) and connect to
it from the Linux VM?

Cheers,
  Steve