Marti Raudsepp wrote:
I will grant you that the details were wrong, but I stand by the conclusion. I can state for a fact that PostgreSQL's default wal_sync_method varies depending on the <fcntl.h> header.
Yes; it's supposed to, and that logic works fine on some other platforms. The question is exactly what the new Linux O_DSYNC behavior is doing, in regards to whether it flushes drive caches out or not. Until you've quantified which of the cases do that--which is required for reliable operation of PostgreSQL--and which don't, you don't have any data that can be used to draw a conclusion from. If some setups are faster because they write less reliably, that doesn't automatically make them the better choice.
-- Greg Smith 2ndQuadrant US greg@xxxxxxxxxxxxxxx Baltimore, MD PostgreSQL Training, Services and Support www.2ndQuadrant.us "PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
