[ZODB-Dev] ZEO client cache tempfile oddness

[Tim Peters]

[Paul Winkler]
>> ...
>> If I understand this stuff correctly, the code in question on a
>> filesystem that *doesn't* have the sparse file optimization would
>> equate to "write N null bytes to this file as fast as possible."
>> True?

[Dieter Maurer]
> Posix defines the semantics.
>
> I have not looked it up, but a possible interpretation would also be:
> write the "n.th" byte and let all other bytes undefined.

POSIX specifies that uninitialized file positions must "act as if"
they contained NUL bytes.  NTFS isn't POSIX, but NTFS in fact does
"write N NUL bytes to the file as fast as possible" for a non-sparse
file (and for a sparse file, NTFS acts like a POSIX file in this
respect).