On Thu, Jan 25, 2018 at 8:32 PM, Tsunakawa, Takayuki <tsunakawa.ta...@jp.fujitsu.com> wrote: > As I showed previously, regular file writes on PCIe flash, *not writes using > PMDK on persistent memory*, was 20% faster with open_datasync than with > fdatasync.
If I understand correctly, those results are all just pg_test_fsync results. That's not reflective of what will happen when the database is actually running. When you use open_sync or open_datasync, you force WAL write and WAL flush to happen simultaneously, instead of letting the WAL flush be delayed. > And you said open_datasync was significantly faster than fdatasync. Could > you show your results? What device and filesystem did you use? I don't have the results handy at the moment. We found it to be faster on a database benchmark where the WAL was stored on an NVRAM device. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
