I found what was causing the difference in timings - it was the Windows disk read cache. If I make sure this cache is clear first (and of course that the GeoWebCache tile cache is also empty), then using either ImageMosaic of a Layer Group takes about the same execution time to generate the tiles. However, if I repeat the test, but this time only clear the GWC tile cache and leave the Windows disk cache untouched, then it seems the Layer Group makes much better use of the cached source images and is much faster than ImageMosaic at generating the tiles again.
Understanding this, it seems ImageMosaic is a good solution for me in practice, as once the tiles have been generated once for an area they will be cached by GeoWebCache anyway so I'll never need to generate them again unless that cache fills up. Many thanks again for your previous help Simone. Tim -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Simone Giannecchini Sent: 14 December 2012 08:40 To: Tim Hayton Cc: [email protected] Subject: Re: [Geoserver-users] How to set InputTransparentColor for MrSid layers? Ciao Tim, can you paste here the gdalinfo output of some of you tiles as well as an indication of the configuration of the parameters in the mosaic layer page in GeoServer? Regards, Simone Giannecchini == Our support, Your Success! Visit http://opensdi.geo-solutions.it for more information. == Ing. Simone Giannecchini @simogeo Founder/Director GeoSolutions S.A.S. Via Poggio alle Viti 1187 55054 Massarosa (LU) Italy phone: +39 0584 962313 fax: +39 0584 1660272 mob: +39 333 8128928 http://www.geo-solutions.it http://twitter.com/geosolutions_it ------------------------------------------------------- On Thu, Dec 13, 2012 at 4:21 PM, Tim Hayton <[email protected]> wrote: > Many thanks for your helpful response Simone, much appreciated. I am now > using an ImageMosaic source which was very easy to do, and as you say it > supports setting of the transparent colour for my MrSid images which works > great. > > One thing I did notice is that it can be slower to generate tile images when > using ImageMosaic when compared to using a Layer Group for the same set of > images. It only seems to be slower though when the requested tiles cover an > area which requires imagery from more than one of the source images. By way > of example, requesting 35 tiles at TMS zoom level 19, all coming from a > single source image, took 5 seconds to serve on my platform with both the > ImageMosaic and Layer Group approaches, but requesting 35 tiles at zoom level > 15, which in this case requires parts from 3 of the source images, takes 65 > seconds using ImageMosaic but only 16 seconds using a LayerGroup. > > I realise the ImageMosaic would have to do some extra work to take the > transparent colour into account at the image borders, so to check this I > tried deleting the InputTansparentColor for the ImageMosaic. This speeded > things up from 65 seconds to 37 seconds, but this is still less than half the > speed of the layer group. I guess the ImageMosaic must also be doing > something extra that the layer group is not. > > As you suggested, I filed a JIRA request for an enhancement for layer groups > to support setting of a transparent colour at > https://jira.codehaus.org/browse/GEOS-5501. > > Regards > > Tim > -- MIRA Ltd Watling Street, Nuneaton, Warwickshire, CV10 0TU, England Registered in England and Wales No. 402570 VAT Registration GB 100 1464 84 The contents of this e-mail are confidential and are solely for the use of the intended recipient. If you receive this e-mail in error, please delete it and notify us either by e-mail, telephone or fax. You should not copy, forward or otherwise disclose the content of the e-mail as this is prohibited. ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Geoserver-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geoserver-users
