Re: Something else about Redo Logs disappearing

On 6/9/20 12:02 PM, Peter wrote:
> On Tue, Jun 09, 2020 at 01:27:20AM -0400, Tom Lane wrote:
> ! Adrian Klaver <adrian.klaver@aklaver.com> writes:
> ! > On 6/8/20 7:33 PM, Peter wrote:
> ! >> That "cp" is usually not synchronous. So there is the possibility
> ! >> that this command terminates successfully, and reports exitcode zero
> ! >> back to the Postgres, and then the Postgres will consider that log
> ! >> being safely away.
> !
> ! > Which is why just following the above command in the docs is:
> ! > "(This is an example, not a recommendation, and might not work on all
> ! > platforms.) "
> !
> ! Yeah.  There have been discussions about changing that disclaimer to be
> ! more forceful, because in point of fact a plain "cp" is generally not safe
> ! enough.  You need to fsync the written file, and on many filesystems you
> ! also have to fsync the directory it's in.
> 
> It certainly does not need to be "more forceful" - because this is not
> about behavioural education, like training dogs, horses, or monkeys,
> and neither do we entertain a BDSM studio.
> 
> What it needs instead is mention of the magic word "fsync". Because,
> we already know that - we just need a reminder at the proper place.
> 
> Systems integrators are professional people. They are not in need of
> more beating (spell: forceful education), only of substantial
> technical hints and informations.
> 
> ! > Generally for peace of mind folks use third party tools like:
> !
> ! +1.  Rolling your own archive script is seldom advisable.
> 
> Well then, using commercial solutions brings it's own problems. E.g.,

FYI, the projects Stephen and I mentioned are Open Source. I'm sure you 
can get paid support for them, but you exist a higher plane then that so 
you can use then for free.

> the people I happened to work for often had problems with torsion,
> which happens when the solution gets longer than, say, twenty meters,
> and these are walked at high speeds.
> 
> They didn't have a problem with scripting - rather the opposite, they
> were happy with it and paid good money for.
> 
> 
> cheerio,
> PMc
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com