WAL contains references to invalid pages - postgresql

Question

centos 6.7
postgresql 9.5.3
I've DB servers that are on master-standby replication.
Suddenly, standby server's postgresql process was stopped with this logs.
2016-07-14 18:14:19.544 JST [][5783e03b.3cdb][0][15579]WARNING: page 1671400 of relation base/16400/559613 is uninitialized
2016-07-14 18:14:19.544 JST [][5783e03b.3cdb][0][15579]CONTEXT: xlog redo Heap2/VISIBLE: cutoff xid 1902107520
2016-07-14 18:14:19.544 JST [][5783e03b.3cdb][0][15579]PANIC: WAL contains references to invalid pages
2016-07-14 18:14:19.544 JST [][5783e03b.3cdb][0][15579]CONTEXT: xlog redo Heap2/VISIBLE: cutoff xid 1902107520
2016-07-14 18:14:21.026 JST [][5783e038.3cd9][0][15577]LOG: startup process (PID 15579) was terminated by signal 6: Aborted
2016-07-14 18:14:21.026 JST [][5783e038.3cd9][0][15577]LOG: terminating any other active server processes
And, master server's postgresql logs were nothing special.
But, master server's /var/log/messages was listed as below.
Jul 14 05:38:44 host kernel: sbridge: HANDLING MCE MEMORY ERROR
Jul 14 05:38:44 host kernel: CPU 8: Machine Check Exception: 0 Bank 9: 8c000040000800c0
Jul 14 05:38:44 host kernel: TSC 0 ADDR 1f7dad7000 MISC 90004000400008c PROCESSOR 0:306e4 TIME 1468442324 SOCKET 1 APIC 20
Jul 14 05:38:44 host kernel: EDAC MC1: CE row 1, channel 0, label "CPU_SrcID#1_Channel#0_DIMM#1": 1 Unknown error(s): memory scrubbing on FATAL area : cpu=8 Err=0008:00c0 (ch=0), addr = 0x1f7dad7000 => socket=1, Channel=0(mask=1), rank=4
Jul 14 05:38:44 host kernel:
Jul 14 18:30:40 host kernel: sbridge: HANDLING MCE MEMORY ERROR
Jul 14 18:30:40 host kernel: CPU 8: Machine Check Exception: 0 Bank 9: 8c000040000800c0
Jul 14 18:30:40 host kernel: TSC 0 ADDR 1f7dad7000 MISC 90004000400008c PROCESSOR 0:306e4 TIME 1468488640 SOCKET 1 APIC 20
Jul 14 18:30:41 host kernel: EDAC MC1: CE row 1, channel 0, label "CPU_SrcID#1_Channel#0_DIMM#1": 1 Unknown error(s): memory scrubbing on FATAL area : cpu=8 Err=0008:00c0 (ch=0), addr = 0x1f7dad7000 => socket=1, Channel=0(mask=1), rank=4
Jul 14 18:30:41 host kernel:
The memory error's started at 1 week ago. So, I doubt the memory error causes postgresql's error.
My question is here.
1) Can memory error of kernel cause postgresql's "WAL contains references to invalid pages" error?
2) Why there is not any logs at master server's postgresql?
thx.

Answer 1

Faulty memory can cause all kinds of data corruption, so that seems like a good enough explanation to me.
Perhaps there are no log entries at the master PostgreSQL server because all that was corrupted was the WAL stream.
You can run
oid2name
to find out which database has OID 16400 and then
oid2name -d <database with OID 16400> -f 559613
to find out which table belongs to file 559613.
Is that table larger than 12 GB? If not, that would mean that page 1671400 is indeed an invalid value.
You didn't tell which PostgreSQL version you are using, but maybe there are replication bugs fixed in later versions that could cause replication problems even without a hardware bug present; read the release notes.
I would perform a new pg_basebackup and reinitialize the slave system.
But what I'd really be worried about is possible data corruption on the master server. Block checksums are cool (turned on if pg_controldata <data directory> | grep checksum gives you 1), but possibly won't detect the effects of memory corruption.
Try something like
pg_dumpall -f /dev/null
on the master and see if there are errors.
Keep your old backups in case you need to repair something!