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I have installed Nominatim to a server dedicated just for OSM data, with the following configurations: CentOS 7 operating system, 2x Intel XEON CPU L5420 @ 2.50GHz (Total 8 CPU cores), 16 GB of ram, and 2x2TB SATA hard drive.

I've configured the postgresql based on the recomendations on the Nominatim install wiki (, taking into account, that my machine has only got 16 GB instead of the 32 GB recommended for those configs. I've used the following things:

shared_buffers = 1GB # recommended for a 32GB machine was 2 GB maintenance_work_mem = 4GB # recommended for a 32GB macinhe was 8 GB work_mem = 20MB # recommended for a 32GB machine was 50 MB effective_cache_size = 10GB # recommended for a 32GB machine was 24 GB synchronous_commit = off checkpoint_segments = 100 checkpoint_timeout = 10min checkpoint_completion_target = 0.9 fsync = off full_page_writes = off

First, I've tried importing a small country extract(Luxembourg), setting a cache size of 6000, using the setup.php file from utils, it was imported succesfully under 1 hour.

Secondly, I've deleted the data of Luxembourg, and imported for another test purpose the country extract of Great Brittain, using a cache size of 8000, it imported succesfully as well, in around 2-3 hours.

Today, I've decided, to try to import the whole planet.pbf file, so I've deleted the postgresql database, downloaded a pbf of the planet from one of the official mirror sites, and ran the setup with a cache size of 10000. Beforehand, I've read up some benchmarks to get a vague idea of how much time and space will this operation take.

When the import started, I was very surprised. The importing of the nodes went with a whopping high speed of 1095.6k/s, in the benchmark which I've analyized (a 32GB ram machine), it was only 311.7k/s.

But when the import of the nodes finished, and the import of the ways started, the speed significantly dropped. It was importing the ways with the speed of 0.16k/s (altough it was slowly rising, it started from 0.05k/s, and in 4 hours it rised to the above mentioned value).

I've stopped the import, and tried to tweak the settings. I've allocated a higher cache size first (12000), but with no success, the nodes imported with a very high speed, but the ways remained at 0.10-0.13k/s. I then tried allocating a new swap file(the original was 8GB, I've allocated another 32GB as a swap file), but that didn't change anything neither. Lastly, I've edited the setup.php, changed the --number-processes from 1, to 6, and included the --slim keyword when osm2psql is started from there, but nothing changed.

Right now I am out of ideas. Is this speed decrease normal? Should I upgrade my machine to the recommended memory? I tought that a 16GB ram would be enough for planet pbf, I was aware that it could take more time with this machine, then with a 32 GB, but this seems very much. If the whole planet import would take not more then 12-15 days, I would be ok with that, but as things look now, with these settings the import would take around 2 months, and this is just too much, considering, an error could occur anywhere, and I have to start the whole import process again.

Any ideas what could cause this problem, or what other tweaks could I try, to fasten the import process?


asked 25 Feb '16, 15:53

Adam%20Baranyai's gravatar image

Adam Baranyai
accept rate: 0%

edited 25 Feb '16, 15:58

There are some parts in the import-process that can not be done in parallel. But have you seen the options: threads and osm2pgsql-cache to speed up the import.

  --threads           Number of threads (where possible)   
  --osm2pgsql-cache   Cache size used by osm2pgsql
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answered 01 Oct '18, 23:42

alfonx's gravatar image

accept rate: 0%

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question asked: 25 Feb '16, 15:53

question was seen: 4,553 times

last updated: 01 Oct '18, 23:42

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum