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

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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