Re: fallocate / posix_fallocate for new WAL file creation (etc...) - Mailing list pgsql-hackers

On 5/30/13 7:13 AM, Andres Freund wrote:
> Why? The spec doesn't specify that case and that very well allows other
> behaviour. Glibc sure does behave sensibly and zeroes the data
> (sysdeps/posix/posix_fallocate64.c for the generic implementation) and
> so does linux' fallocate() syscall, but that doesn't say much about
> other implementations.

glibc actually only writes one byte to every file system block, to make
sure the block is allocated.  It doesn't actually zero every byte.