Mapserver performance issue: why so much slower?

[Brent Wood]

Hi,

I have prototyped some background map data to be served by Mapserver. There are
about 7Gb of Postgis data and 4Gb of images, The images comprise 3 zoom layers,
of 2, 100 & 800 tiles each, each addressed via a shapefile tileindex. Just
using the basic CGI mapserv application & a mapfile.

The prototype system is an AMD 64bit 3500+ cpu, with 1Gb memory & 2 80Gb SATA
drives. The PostGIS database is on a software RAID0 partition with a nominal
100Mb/sec I/O. It is running SUSE 9.3 A64 with all the GIS related apps
compiled from scratch so they are all 64bit apps. I'm more than pleased with
the performance.

I have only ftp & remote Postgres access to the production server...
(don't ask !!!!! :-) so am limited in what I can do (even more than my normal
limitations).

The server this is to be implemented on is running a Java digital asset
management application as an image database under Windows 2k3 server. Mapserver
is implemented only as a Java mapscript capability, embedded in the
application, to provide a location based facility for selecting images. 

The server is supposedly an Intel 3.5Ghz hyperthreaded cpu with 3.5Gb memory &
a reasonable SCSI RAID array. Postgres performance seems fine, so I don't think
it is a database performance issue (but I could be wrong about this- our tests
have been not been for large geometry objects such as are retrieved by
mapserver, but for large numbers of small tuples)

Mapserver, however, is very slow. It is taking about 5x as long to render the
maps with only 20% of the data being implemented in the mapfile & no rasters.

Also, unlike the Linux box, repeat accesses/redraws do not speed up compared to
the original (Linux vs Windows caching perhaps?)

Does anyone have any suggestions/ideas about the performance of Java mapscript
vs cgi mapserver, Linux 64bit vs Windows 32bit, Intel vs AMD, etc. There are so
many points of difference, & I'd like to narrow my search for the basic
cause/solution if at all possible.

We may be able to stick a Linux A64 box as the postgis/mapserver server, but if
it is a Java mapscript vs CGI mapserve issue, this may not do anything to help.

Running a separate WMS Linux mapserver server & the image db as a Javascript
WMS client will (as I understand it) remove virtually all the load from the
Windows box, so may be a suitable solution. Any comments on this approach? Is
it feasible with Java mapscript? 


Thanks,

   Brent Wood