Mapserver on Linux vs Windows

[Ed McNierney]

Tim -

Thanks for filling in some of the details - sounds like quite a project!

If all your data are coming from external SDE sources, outside of your
control, then don't worry about those.  Pay attention to the
configuration of your MapServer systems.

In your scenario, your MapServer systems will all be acting as OGC
clients and servers.  In those scenarios, those machines will be doing a
lot of disk I/O, writing data retrieved from the SDE boxes and then
reading that data to build and serve output data.  As a result, you will
have a lot of simultaneous reading and writing going on.  Each system
will have a very busy disk subsystem.

You will want a disk subsystem that has very low random seek times
(since you'll be jumping around among multiple requests all the time),
and can handle lots of simultaneous I/O requests.  Conversely, all your
MapServer data is transient data used only to serve the current request,
so you don't need to worry about redundancy or disk failure on your data
disks.

That sounds like a recipe for (a) a RAID 0 (striped) array of disks, (b)
SCSI drives, and (c) high-RPM disks.  The RAID 0 array will give you
excellent read and write performance.  It will give you no data
redundancy, but you don't care about that.  You should opt for a large
number of smaller disks rather than a small number of larger disks, as
this will improve your performance.  SCSI drives will handle multiple
I/O requests better than IDE drives.  And high-RPM drives (15K RPM) will
reduce your seek times (and are another reason to use SCSI, as SCSI
drives are generally available at higher RPMs).

The chief downside of this architecture is that it's expensive.  From
your description of the project, it doesn't sound like that's a problem
<g>.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed at topozone.com
(978) 251-4242 

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Tim Bowden
Sent: Monday, March 06, 2006 9:27 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] Mapserver on Linux vs Windows

On Sun, 2006-03-05 at 12:45 -0500, Ed McNierney wrote:
> Tim -
> 
> Sounds like a good plan.  The biggest variable (assuming the hardware
is the same) is the layout of your data sources.  It's important to
think those through to get the best performance.
> 

Ed, Could you elaborate on the 'layout of your data sources' bit.  All
our data is in various sde boxes.  Given the dispersed nature of our
data sets (geographically and custodianship) we don't have much leeway
as to how we can set things up; All sde boxes are behind on site
mapserver ogc client boxes which in turn act as ogc servers to a central
mapserserver which will be accessible to authorised users.

> The other thing to keep in mind is where your shop's expertise lies.
Do you have equal skills and experience with both operating systems?  If
not, it is likely to be a good idea to stick with what you know.  That's
how I generally advise users who ask "should I use Windows or Linux"?  I
have yet to see an apples-to-apples comparison that showed any
significant difference between the two operating systems.  But the
effort and expense associated with learning or trying to manage an OS
you don't know probably outweigh any potential performance differences.
> 

This project is being run by a consortium led by Computer Associates so
almost any skill you can think of is here somewhere ;-)  It's big enough
that the client will have a gis/IT admin team assigned to the project.
Whatever skills are missing will be acquired by the client in due
course.  It's a whole of govt approach to gis data dissemination which
is made all the more exciting by the central spot held by GIS FOSS.

>      - Ed


Tim Bowden

--
Mapforge Geospatial
Level 3/ 267 St Georges Tce
Perth 6000
Western Australia