[postgis-users] Shared memory extesion on a a Mac for PostgreSQL/PostGIS
scottso at sonalysts.com
Tue Mar 8 05:28:25 PST 2011
I've several systems with 8-24 GB of RAM running postgres and postgis. I built postgres as a 64-bit executable to take advantage of the larger address space. As a rule for databases, they are memory hungry. I generally follow: effective cache size, 50% RAM; shared_buffers, 25% RAM. There are other PG tuning parameters available in performance docs/discussions on the web.
With only 2GB of RAM, the bit-width of postgres shouldn't matter, and your setting of 1.5 GB shmmax seems a little too large. Try keeping it below 1.25 GB, or even 1 GB. Since you said this is only a prototype, performance shouldn't be a top priority. You also don't want to starve the OS of resources. Consider starting with your postgres setting half or even a quarter of what I stated above. Also, consider lowering the max_connections setting; each connection requires more shared memory. This way you can also limit the size of your kernel resources.
You can also dynamically change the kernel parameters with `sysctl -w PARAMETER=VALUE` from the command line to find a setting you're comfortable with before committing it to /etc/sysctl.conf. The only reason to have large memory space for postgres is to store as much of the database as possible in memory, i.e., faster access and less/no swapping.
As for the pgAdmin question, it's a good tool, but it ultimately comes down to what you're comfortable with. I prefer the command line.
Hope that clears things up at least a bit.
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Scott Brunza 860.326.3637 scottso at sonalysts.com
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