[mapserver-users] WMS Orthophoto performance
mwkorver at gmail.com
Mon Aug 2 15:24:47 EDT 2010
Many things come into play to make the response time of MapServer long
or short. But at a basic level the time required to get just the part
of the image required in the source file(s) and the CPU time required
to decode that part if compressed, are major factors in performance.
ECW is wavelet, and I maybe wrong but nowadays I think that means its
just jp2 from the perspective of GDAL so its not going to be fast in
comparison to other formats like GTIF. That just because decoding the
jp2 just takes a lot more time than say decoding GTIF with jpeg
I know from other sid file based projects that I have done, something
like 3 seconds would not be surprising, especially if you are talking
a largish image and travel time to browser. Our only solution to that
to achieve any real speed was to go to a TMS structure (now WMTS)
using jpeg. which means you go to about 5-6 compression ratio rather
than 15 as you would get from jp2.
so your 150GB would be more like 500GB? But a lot faster.
2010/8/2 Cédric MOULLET <cedric.moullet at gmail.com>:
> Hi Andy,
> Thanks for your answer.
> The dataset is composed of several ECW files, that's why we use TILEINDEX.
> The data are hosted on EBS (http://aws.amazon.com/ebs/). It's supposed to
> have normal I/O performance, but probably not fantastic performance. Of what
> I have observed, I would say that the CPU is probably the bottleneck.
> My goal is to have a 1s response time. Do I dream too much ?
> 2010/8/2 Andy Colson <andy at squeakycode.net>
>> On 8/2/2010 5:06 AM, Cédric MOULLET wrote:
>>> We've got a 150 GB ECW dataset (aerial imagery) and the LAYER
>>> configuration uses a TILEINDEX.
>>> We can observe a WMS request time of about 3 seconds (on a server with
>>> this configuration: 7.5 GB RAM, 4 core, 64 bits / MapServer 5.4.3).
>>> I'd like to know if 3 seconds is considered as a normal response time
>>> for this kind of WMS request.
>>> What could be done in order to improve this performance (I'm aware of
>>> http://www.mapserver.org/optimization/raster.html) ?
>>> Thanks !
>> Wow, that's a big file. Is that all in one file? I dont really know the
>> answer, I've never used anything over 4 gig, but I do have a few questions:
>> 1) I assume you are IO bound, do you have this on a raid, or something
>> with fast IO? Can you check to see if you are CPU bound or IO bound?
>> 2) if it is one big file, how would you feel about trying it broken up
>> into smaller files?
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