Paul Norman wrote 2014-06-18 19:44:
The Imposm presentation states that larger extracts in osm2pgsql
require comparable resources to a full planet import due to the cache
structure used. Having not observed this when importing, I collected
the data to test it while performing an import of the Germany
Geofabrik extract from June 1st. At a size of 2.2GB (10^9 bytes/GB),
this is a large extract.
osm2pgsql reports the storage efficiency of the node cache, in this
case 51.85%. This is a typical efficiency for extracts.
This works out to a minimum memory of 2.7GB to keep all nodes in the
memory cache. It is of course possible to import with less, but then
osm2pgsql will fetch node locations from the database. I would
generally question if a machine with under 4GB of RAM is suitable for
rendering such a large area, regardless of OSM to database conversion
tools used.
OSM data are not only used for rendering. With GDAL I can easily import
germany-latest.osm.pbf into PostGIS on a hosted server with only 700 MB
of RAM and it is perfectly suitable for serving data out through WFS
service. I do use the same machine for rendering into WMS with Mapserver
and it works also but honestly, it is not very fast. PostgreSQL+PostGIS
runs also on the same tiny server. Importing with osm2pgsql is not
possible and if I want to play with osm2pgsql tables I must do import
with home computer and transfer the tables with pgdump/restore which is
not very handy but with my budget I must tolerate it.
-Jukka Rahkonen-
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