[ka-Map-users] Precaching, metatiling, and mapserver

Justin George justin.george at gmail.com
Wed May 17 19:15:34 EDT 2006

I've been delving into precacheing more deeply here lately, and I have
a couple questions that should be fairly simple if people are doing
the same thing I am (precaching the entire extents of the map data to
be rendered)

A) Which is faster, large metatiles or small metatiles?
Right now I've increased the size, which seems to give faster
generation. Using 800x800 tiles at 4x4 per metatile looks to be giving
me about 30% speed increase.

B) Is there a good reason to delete the metatiles besides the space requirement?
I'm currently not running anywhere near my space limits (3gb of a
120gb array) so I'm curious whether unlinking the metatiles helps
anything, or whether I can turn it off to not have to regenerate them

C) What seems to be the slowest part of precaching?
To me it's looking like the initial generation, but I'm curious
whether cutting the tiles up takes a substantial amount of time, as
well. If they don't, then (barring some inherent limit) it seems that
I should ramp the metaWidth and metaHeight up even further, while
keeping the tile sizes themselves small for faster downloading.

Also, I should specify I'm running this on a linux-based box, with
most of the data coming from tileindexed shapefiles, but some still
being pulled from postgres with PostGIS on it (trying to transition
away from that, as it appears to be slower)

Thanks for the help, folks!

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