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Re: [ADMIN] openvz and shared memory trouble

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On 03/29/2014 08:19 AM, Willy-Bas Loos wrote:
The error that shows up is a Bus error.
That's on the replication slave.
Here's the log about it:
2014-03-29 12:41:33 CET db: ip: us: FATAL:  could not receive data from
WAL stream: server closed the connection unexpectedly
         This probably means the server terminated abnormally
         before or while processing the request.

cp: cannot stat
`/data/postgresql/9.1/main/wal_archive/00000001000000720000000A': No
such file or directory
2014-03-29 12:41:33 CET db: ip: us: LOG:  unexpected pageaddr
71/E9DA0000 in log file 114, segment 10, offset 14286848
cp: cannot stat
`/data/postgresql/9.1/main/wal_archive/00000001000000720000000A': No
such file or directory
2014-03-29 12:41:33 CET db: ip: us: LOG:  streaming replication
successfully connected to primary
2014-03-29 12:41:48 CET db: ip: us: LOG:  startup process (PID 17452)
was terminated by signal 7: Bus error
2014-03-29 12:41:48 CET db: ip: us: LOG:  terminating any other active
server processes
2014-03-29 12:41:48 CET db:wbloos ip:[local] us:wbloos WARNING:
terminating connection because of crash of another server process
2014-03-29 12:41:48 CET db:wbloos ip:[local] us:wbloos DETAIL:  The
postmaster has commanded this server process to roll back the current
transaction and exit, because another server process exited abnormally
and possibly corrupted shared memory.
2014-03-29 12:41:48 CET db:wbloos ip:[local] us:wbloos HINT:  In a
moment you should be able to reconnect to the database and repeat your
command.


Well what I am seeing are WAL log errors. One saying no file is
present, the other pointing at a possible file corruption. Shared memory problems are offered as a possible cause only. Right now I would say we are seeing only half the picture. The Postgres logs from the same time period for the primary server, as well as the system logs for the openvz container would help fill in the other half of the picture.





On Fri, Mar 28, 2014 at 2:52 PM, Adrian Klaver
<adrian.klaver@xxxxxxxxxxx <mailto:adrian.klaver@xxxxxxxxxxx>> wrote:


    25% is a suggested value, not an absolute value. Desirable would
    seem to be a value that works for your situation and maintains
    performance. Is there any indication that running with a lower value
    adversely affects performance?




Thanks, i'm looking into the bean counters more.
Maybe there is something to won by guaranteeing the shared memory
resources, instead of just refraining from constraining them.



Ok, that sounds reassuring, and i agree that the other posts are not
really related. It's just that i found several posts that boiled down to
memory related issues with openVZ, and experts complaining. That made me
worry.

A cursory look at memory management in openvz shows it is different from other virtualization software and physical machines. Whether that is a problem would seem to be dependent on where you are on the learning curve:) As to 'experts' complaining, I have heard a lot of that in many different fields and every once in while they are right, so it tends to be low on my check list when it comes to doing things.


--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx


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