Re: why not kill -9 postmaster

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Shane Ambler <pgsql(at)007Marketing(dot)com>, Andreas Seltenreich <andreas+pg(at)gate450(dot)dyndns(dot)org>, pgsql-general(at)postgresql(dot)org
Subject: Re: why not kill -9 postmaster
Date: 2006-10-20 14:18:41
Message-ID: 8058.1161353921@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Shane Ambler wrote:
>> The one thing worse than kill -9 the postmaster is pulling the power
>> cord out of the server. Which is what makes UPS's so good.
>>
>> If your server is changing the data file on disk and you pull the power
>> cord, what chance do you expect of reading that data file again?

> 1. That's what we have WAL for. The only thing that can really kill
> you is the use of non-battery-backed write cache.

The important distinction here is "will you lose data" vs "can you start
a new server without tedious manual intervention" (ipcrm etc). kill -9
won't lose data, but you may have to clean up after it. And, as Andreas
already noted, some people have been seen to mess up the manual
intervention part badly enough to cause data loss by themselves.
Personally I think the TIP that's really needed is "never remove
postmaster.pid by hand".

regards, tom lane

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