Re: [HACKERS] Postgres Speed or lack thereof

Tom Lane wrote:
>
> Vadim Mikheev <vadim(at)krs(dot)ru> writes:
> > Tom Lane wrote:
> >> However, with a UPS and an OS that only crashes about once every
> >> other year, I feel pretty secure using -F ...
>
> > However, it's easy to crash Postgres itself and lose
> > committed transactions -:(
>
> Surely not? The docs say (and a quick look at the code confirms)
> that -F suppresses calls to fsync(2). It does not suppress writes.
> Thus, a commit will still write the data out to kernel disk buffers.
> All that fsync does is force the kernel to execute immediate disk
> writes for those buffers. If I don't fsync, and the backend crashes,
> the modified file data is still in kernel disk buffers and the kernel
> is still responsible for seeing that those dirty buffers get written
> out eventually.

You're right.

Vadim