Re: how unsafe (or worst scenarios) when setting fsync OFF for postgresql

"Guoping Zhang" <guoping.zhang@nec.com.au> writes:
> Our application has a strict speed requirement for DB operation. Our tests
> show that it takes about 10secs for the operation when setting fsync off,
> but takes about 70 seconds when setting fsync ON (with other WAL related
> parametered tuned).

I can't believe that a properly tuned application would have an fsync
penalty that large.  Are you performing that "operation" as several
thousand small transactions, or some such?  Try grouping the operations
into one (or at most a few) transactions.  Also, what wal_buffers and
wal_sync_method settings are you using, and have you experimented with
alternatives?   What sort of platform is this on?  What PG version?

            regards, tom lane