Обсуждение: Re: Re: Idea: recycle WAL segments, don't delete/recreate 'em

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> Hi -
> 
> pgman wrote:
> 
> : Most Unix filesystems will not allocate disk blocks until you write in
> : them.  [...]
> 
> Yes, I understand that, but how is it a problem for postgresql?

Uh, I thought we did that so we were not allocating file system blocks
during WAL writes.  Performance is bad when we do that.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026
 

Bruce Momjian wrote:
>
> Checking application/pgp-signature: FAILURE
> -- Start of PGP signed section.
> > Hi -
> >
> > pgman wrote:
> >
> > : Most Unix filesystems will not allocate disk blocks until you write in
> > : them.  [...]
> >
> > Yes, I understand that, but how is it a problem for postgresql?
>
> Uh, I thought we did that so we were not allocating file system blocks
> during WAL writes.  Performance is bad when we do that.
   Performance isn't the question. The problem is when you get a   "disk full" just in the middle of the need to write
important  WAL  information. While preallocation of a new WAL file, it's   OK and controlled, but there are more
delicate portions  of   the code.
 


Jan

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