> -----Ursprüngliche Nachricht----- > Von: Tom Lane [mailto:tgl@xxxxxxxxxxxxx] > Gesendet: Montag, 29. Mai 2017 10:19 > An: Klaus P. Pieper > Cc: pgsql-admin@xxxxxxxxxxxxxx > Betreff: Re: pgbench Windows outperforms Debian in Write tests > while Debian is faster in SELECT only tests > > "Klaus P. Pieper" <kpi6288@xxxxxxxxx> writes: > > How can Windows outperform Debian by a factor of 2? > > Are you sure you have Windows configured to fsync properly? > Not waiting for writes to hit disk would be a really easy explanation for a > discrepancy of this kind. It seems that it is indeed related to the wal_sync_method settings. Results for 1 client read / write: Option Windows Debian fdatasync 340 150 fsync 125 90 open_datasync 360 160 fsync_writethrough 115 n/a open_sync n/a 90 fsync = off 360 400 The result setting fsync=off shows that the maximum performance of the Debian syste is above Windows. However, with fsync=on, Windows still outperforms the Debian system with all options. In addition, the results on the Windows system with “fsync = off” are the same as “wal_sync_method = open_datasync” What does this mean? - Is the Windows system “better” than the Debian system? - Or is the underlying filesystem on the Windows system less safe? - Or is the Windows system better integrated with the Hyper-V host? The Windows systems reports that the write cache is switched on for the virtual disk. It is however not possible to switch is off. Thanks Klaus |
