Merlin Moncure wrote:

> After last night, I rebuilt the cluster, turning on checksums, turning
> on synchronous commit (it was off) and added a standby replica.  This
> should help narrow the problem down should it re-occur; if storage is
> bad (note, other database on same machine is doing 10x write activity
> and is fine) or something is scribbling on shared memory (my guess
> here)  then checksums should be popped, right?

Not really sure about that.  As I recall we compute the CRC on the
buffer's way out, based on the then-current contents, so if something
scribbles on the buffer while it's waiting to be evicted, the CRC
computation would include the new (corrupted) bytes rather than the
original ones -- see FlushBuffer.

Álvaro Herrera      
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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