| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: emergency outage requiring database restart |
| Date: | 2016-10-25 17:57:27 |
| Message-ID: | 20161025175727.p25f3h5dq5bgggye@alvherre.pgsql |
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| Lists: | pgsql-hackers |
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 https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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