[mapserver-users] Try Again ... Large scale implementation

[Paul Ramsey]

Chris Casad wrote:

> I have seen a lot of threads about which is better ArcIMS or MapServer. And
> from what I have read MapServer is faster. But is that a simple one to one
> request comparison, where MapServer just draws a map faster?  

1) Yes, that is the fundamental unit of comparison. Based on the same
data, which system requires more effort to get the fundamental result (a
map).

> If I have
> 100's of hits per second do I need to have 50 more servers to handle these
> requests than ArcIMS would need?  If so then it would probably be cheaper to
> pay for ArcIMS and to not have to deal with a large number of servers?
> Correct? 

2) No, because ArcIMS is an order of magnitude more expensive than a new
computer. The software cost actually dwarfs the hardware cost. 

> Unfortunately I haven't noticed any threads about anyone using
> MapServer for large-scale implementations (hence my thread).  Also, I know
> that ArcIMS is somewhat easily scaleable if your hit counts increase. Can
> MapServer be just as easily scaleable if the need arises or is there a lot
> more coding you would have to do?

The scaling effect of 1) is that the CPU-required-per-hit for a
mapserver installation is lower than for an IMS installation. For a
large installation, the differential only magnifies. IMS marketing folks
might say that because they are long-run multi-threaded they can scale
better into high hit ranges, but they only get X amount of performance
advantage from that. If they are also burning CPU in ineffecient
rendering (as they are) they'll end up losing all the speed advantage
their architecture is supposed to give them. And as an added bonus, the
long-run aspect of IMS makes it less fault tolerant -- if you crash
ArcIMS, the whole thing is toast. If you crash Mapserver, you lose just
the one rendering instance.

As far as scaling up, Steve has in the past pointed out some ultra
simple load balancing tricks. A single simple front-end perl script can
redirect map requests to a whole farm of mapserver hosts.

All of which still fails to answer your fundamental question about an
existing high-volume site. I would feel perfectly safe setting up a
high-volume site under mapserver, but I do not have an example to offer
you :(


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     | Paul Ramsey
     | Refractions Research
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