Re: fsync = true beneficial on ext3?

On Sun, 8 Feb 2004, Ed L. wrote:

>
> I'm curious what the consensus is, if any, on use of fsync on ext3
> filesystems with postgresql 7.3.4 or later. I did some recent performance
> tests demonstrating a 45%-70% performance improvement for simple inserts
> with fsync off on one particular system. Does fsync = true buy me any
> additional recoverability beyond ext3's journal recovery?
>
> If we write something without sync'ing, presumably it's immediately
> journaled? So even if the DB crashes prior to fsync'ing, are we fully
> recoverable? I've been running a few pgsql clusters on ext3 with fsync =
> false, suffered numerous OS crashes, and have yet to lose any data or see
> any corruption from any of those crashes. Have I just been lucky?

With all the other posts on this topic, I just want to point out that it's
all theory until you build your machine, set it up, initiate a hundred or
so parallel transactions, and pull the plug in the middle.

Without pulling the plug, you just don't know for sure. And you need to
do it a few times, in case your machine "got lucky" once and might fail on
subsequent power fails.