On 2018-02-20 00:27:47 +0000, Tsunakawa, Takayuki wrote:
> I propose changing the default value of wal_sync_method from fdatasync
> to open_datasync on Linux.  The patch is attached.  I'm feeling this
> may be controversial, so I'd like to hear your opinions.

Indeed. My past experience with open_datasync on linux shows it to be
slower by roughly an order of magnitude. Even if that would turn out not
to be the case anymore, I'm *extremely* hesitant to make such a change.

> [HDD on VM, ext4 volume mounted with noatime,nobarrier,data=writeback]
> (the figures seem oddly high, though; this may be due to some VM
> configuration)

These numbers clearly aren't reliable, there's absolutely no way an hdd
can properly do ~30k syncs/sec.  Until there's reliable numbers this
seems moot.


Andres Freund

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