Re: Recommended value for pg_test_fsync

On Tue, Jun 30, 2020 at 1:02 AM Nikhil Shetty <nikhil(dot)dba04(at)gmail(dot)com>
wrote:

> Hi Bruce,
>
> Based on pg_test_fsync results, should we choose open_datasync or
> fdatasync as wal_sync_method? Can we rely on pg_test_fsync for choosing the
> best wal_sync_method or is there any other way?
>

Probably the default of fdatasync. The place where pg_test_fsync would
tell me not to use fdatasync is if it were so fast that it was not credible
that it was honestly syncing the data. I don't think pg_test_fsync does a
good job of exercising the realistic differences between fdatasync and
open_datasync. So unless it shows that one of them is lying about the
durability, it doesn't offer much help.

Cheers,

Jeff