Re: full_page_writes on SSD?

On 2015-11-24 13:09:58 -0600, Kevin Grittner wrote:
> On Tue, Nov 24, 2015 at 12:48 PM, Marcin Mańk <marcin(dot)mank(at)gmail(dot)com> wrote:
>
> > if SSDs have 4kB/8kB sectors, and we'd make the Postgres page
> > size equal to the SSD page size, do we still need full_page_writes?
>
> If an OS write of the PostgreSQL page size has no chance of being
> partially persisted (a/k/a torn), I don't think full page writes
> are needed. That seems likely to be true if pg page size matches
> SSD sector size.

At the very least it also needs to match the page size used by the OS
(4KB on x86).

But be generally wary of turning of fpw's if you use replication. Not
having them often turns a asynchronously batched write workload into one
containing a lot of synchronous, single threaded, reads. Even with SSDs
that can very quickly lead to not being able to keep up with replay
anymore.