hardware

[Ed McNierney]

Brent -

I have to disagree with such a sweeping generalization concerning Windows and Linux servers.  Having run both Windows and Linux servers for MapServer, MySQL, PostGIS and other applications for several years, I find it hard to claim that on identical hardware one is noticeably faster or slower than the other.  Your mileage can (and obviously does) vary, but since you're running on two different machines your "inferior" system may well be better suited to the load you're giving it than the Windows system.  I'm sure there are exceptions, and applications where there IS a noticeable difference between otherwise identical systems, but my experience does not show that a broad statement based on your observations on one pair of servers is warranted.

First, the load Kim is talking about is quite light.  If there are 200 hits per hour, and a 3x increase is expected, that's 600 hits per hour or 10 hits per minute; one hit every six seconds.

Second, I think it's very important to separate the MapServer and PostGIS portions of the application, at least for discussion purposes.  The optimal arrangement for each application may not be the same, and there may need to be some compromise if they're to run on one system.

Third, I do agree that fast RAID 5 disks and lots of RAM are always a good idea!

Finally, I think the most important think to remember is to work with what you know.  If your staff are accustomed to and trained in using Windows systems, moving to Linux is hard and expensive - in terms of training, consultants, time to resolve issues, etc.  The reverse is equally true.  There is a high cost of moving to an operating system environment you don't know, and there needs to be a very good reason why you're willing to incur that cost.  The suggestion that Kim "go to Linux ASAP" is a very expensive suggestion if the needed Linux skills aren't available.  IMHO, the first step is to ensure optimal hardware design using the operating system Kim's most familiar with.

	- Ed

Ed McNierney
Chief Mapmaker
Demand Media / TopoZone.com
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: 978-251-4242, Fax: 978-251-1396
ed at topozone.com

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On Behalf Of Brent Wood
Sent: Tuesday, January 08, 2008 4:32 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] hardware

--- Kim Allen <walker1145 at QWEST.NET> wrote:

> I have been given the chance to spec out a server for our mapserver and need
> some help to take advantage of this. What I would like to do is to run
> mapserver on apache using  postgresql/postgis as the database. I anticipate
> using only a few shapefiles  for state /province boundaries and all of the
> rest on the postgres database. On that spatial database I have a table with
> 1.6 million entries, another with 180,000 entries updated daily and both of
> these are points, I will also have several tables with ploygons. I am using
> an html template for the maps but would like to use an interface like ka-map
> down the road. Currently I am using about 68 GB of disk space out of 138 GB
> however after the upgrade I would like to start adding some raster images.
> The peak number of hits an hour are around 200 but I know that will go up
> with an increase of speed. Since we are a MS shop I am looking for something
> that should be able to handle at least 3 times the number of hits per hour
> running on a MS server. However I also anticipating migrating to a linux
> based solution in the immediate future but for now I have to satisfy the
> powers that be.
> 
> Any suggestions based upon the sketchy outline above will be appreciated.

Hi Kim,

Having wrestled with an unacceptably slow Windows server, and a much faster
Linux system, despite being on inferior hardware (we still run the Windows
server with a java mapscript client, but have abstracted PostGIS/Mapserver to a
separate Linux server - using WMS - about 400 miles from the Wndows box), my
first comment would be to go Linux ASAP.

I think you'll get more benefit properly configuring Postgres & indexing,
partitioning & clustering your PostGIS tables & perhaps using fastcgi for
mapserver than tweaking hardware.   

I have compared the same PostGIS database under Linux & Windows on the same
hardware, using in one case a 1.6m row table with points, lines & polygons.

The first (moderately complex) query took about 18 secs on both systems after
rebooting. Repeating the query took 18 secs again on the Windows box, but 3
under Linux. Linux file caching & Postgres seem a much better match than under
Windows.

As far as hardware goes, fast raided disks, striped if data security isn't a
huge issue & price is, or a more sophisticated raid 5, perhaps 0+1 if redundant
disks are required.

I have found AMD cpu's outperform Intel $ for $ in this sort of application,
but your mileage may vary. As much memory as you can afford is probably going
to help more than sheer cpu speed, or number of cores.

So my advice, worth all that I'm charging for it, spend your budget of the
fastest disks, as much memory & as much cpu as you can afford, in that order,
for Windows.

For Linux, with its superior file caching, I'd suggest the same, but put memory
first, as lots of memory will make up for (slightly) slower disks.

To make best use of all that memory, a 64bit OS is prefereable.

Enough memory to cache the entire database would be a good starting point,
there have been discussions on the Postgres user list about running it in a ram
disk for sheer speed, but if it fits in memory anyway, then the OS should do
that for you. 

You might also look at OpenLayers instead of Ka-Map! for your interface, it's
ability to cache clientside layers & download tiles, while a bit slower to
start, is much faster overall in my experience.


Cheers,

  Brent Wood