2 ms·
> 32GiB read only: read only test, the dataset does not fit into the PostgreSQL cache > 200GiB read only: read only test, the dataset fits into the PostgreSQL
by Fiahil 9y ago
> 32GiB read only: read only test, the dataset does not fit into the PostgreSQL cache
> 200GiB read only: read only test, the dataset fits into the PostgreSQL cache
How come a larger dataset fit into the PostgreSQL cache and not the smaller one ?
- belthesar 9y agoI wondered the same thing. Best explanation had to do with the 32 GB dataset being on the system with 32 GB of RAM vs the 200 GB dataset on the system with 256 GB of RAM. Makes sense, but isn’t clear from the article’s perspective.
- elygre 9y agoProbably different postgresql.conf-settings. For example, 32GiB instance has "effective_cache_size = 24GB", while 200GiB instance has "effective_cache_size = 144GB"
- lazyjones 9y agoThey used 2 different servers. One with 32GB RAM, the other with 256GB.
- ianai 9y agoThat might explain the first results. ZFS eats ram (to good use).
- kovacik 9y agoThe size of postgresql database was ~74GB for every test combination. The bare metal server had 256GB RAM for every test combination. The only difference was the amount of RAM PostgreSQL could use - as specified in postgresql.conf. So, 74GB database does not fit in PostgreSQL cache for 32GB instance and fits for 200GB instance.