On 11/29/2015 02:41 PM, Craig Ringer wrote:
On 27 November 2015 at 19:17, Tomas Vondra <tomas.von...@2ndquadrant.com
<mailto:tomas.von...@2ndquadrant.com>> wrote:

    It's also possible to mitigate this by setting wal_sync_method=fsync

Are you sure?

https://lwn.net/Articles/322823/ tends to suggest that fsync() on the
file is insufficient to ensure rename() is persistent, though it's
somewhat old.

Good point. I don't know, and I'm not any smarter after reading the LWN article. What I meant by "mitigate" is that I've been unable to reproduce the issue after setting wal_sync_method=fsync, so my conclusion is that it either fixes the issue or at least significantly reduces the probability of hitting it.

It's pretty clear that the right fix is the additional fsync on pg_xlog.


Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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