Re: Available disk space per tablespace

Re: Quan Zongliang
> According to the statvfs documentation for macOS
> f_frsize       The size in bytes of the minimum unit of allocation on this
> file system.
> f_bsize        The preferred length of I/O requests for files on this file
> system.

Thanks for catching that. f_frsize is the correct field to use. The
statvfs(3) manpage on Linux has it as well, but it's less pronounced
there so I missed it:

          struct statvfs {
               unsigned long  f_bsize;    /* Filesystem block size */
               unsigned long  f_frsize;   /* Fragment size */
               fsblkcnt_t     f_blocks;   /* Size of fs in f_frsize units */
               fsblkcnt_t     f_bfree;    /* Number of free blocks */
               fsblkcnt_t     f_bavail;   /* Number of free blocks for
                                             unprivileged users */


> In addition, many systems use 1000 as 1k to represent the storage size.
> Shouldn't we consider this factor as well?

That would be a different pg_size_pretty() function, unrelated to this
patch.

I'm still unconvinced if we should use statfs() instead of statvfs()
on *BSD or if their manpage is just trolling us and statvfs is just
fine.

DESCRIPTION
       The statvfs() and fstatvfs() functions fill the structure pointed to by
       buf  with  garbage.  This garbage will occasionally bear    resemblance to
       file system statistics, but portable applications must  not  depend  on
       this.

Christoph