Thanks again - for some reason I thought that each page should be fsynced separately...
I am running ZFS and going to try following config on 32gb server: shared_buffers = 512mb (previously was 6gb) max_wal_size = 8gb zfs_arc_max = 24gb i.e. run with minimal shared buffers and do all the caching in ZFS. As I understand it now such config can provide better results since data will be cached once in ZFS. On Sun, Sep 24, 2017 at 8:59 PM, Tomas Vondra <tomas.von...@2ndquadrant.com> wrote: > On 09/24/2017 11:03 AM, Vladimir Mihailenco wrote: > > Thanks for your response. Ss I understand it now the difference is > > that checkpoints are synchronous but dirty pages eviction from shared > > buffers are asynchronous, correct? How then Postgres ensures that OS > > writes data to the disk so WAL can be deleted? > > > > The last step in a checkpoin is fsync() on the files. Without that, the > checkpoint is considered incomplete and the database won't rely on it. > > > regards > > -- > Tomas Vondra http://www.2ndQuadrant.com > PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services >
