Hi, On 2018-04-28 08:25:53 -0700, Simon Riggs wrote: > > - Use direct IO. Due to architectural performance issues in PG and the > > fact that it'd not be applicable for all installations I don't think > > this is a reasonable fix for the issue presented here. Although it's > > independently something we should work on. It might be worthwhile to > > provide a configuration that allows to force DIO to be enabled for WAL > > even if replication is turned on. > > "Use DirectIO" is roughly same suggestion as "don't trust Linux filesystems".
I want to emphasize that this is NOT a linux only issue. It's a problem across a number of operating systems, including linux. > It would be a major admission of defeat for us to take that as our > main route to a solution. Well, I think we were wrong to not engineer towards DIO. There's just too many issues with buffered IO to not have a supported path for DIO. But given that it's unrealistic to do so without major work, and wouldn't be applicable for all installations (shared_buffer size becomes critical), I don't think it matters that much for the issue discussed here. > The people I've spoken to so far have encouraged us to continue > working with the filesystem layer, offering encouragement of our > decision to use filesystems. There's a lot of people disagreeing with it too. Greetings, Andres Freund
