Mark Mielke wrote:
> Is there anything in POSIX that seems to suggest this? :-) (i.e. why
> are you going under the assumption that the answer is yes - did you
> read something?)
>
It was something somewhere on the Sun web site, relating to tuning Solaris
filesystems. Or databases. Or ZFS. :-(
Needless to say I can't find a search string that finds it now. I
remember being surprised
though, since I wasn't aware of it either.
> I don't believe POSIX has any restriction such as you describe - or if
> it does, and I don't know about it, then most UNIX file systems (if
> not most file systems on any platform) are not POSIX compliant.
That, I can believe.
>
> Linux itself, even without NCQ, might choose to reorder the writes. If
> you use ext2, the pressure to push pages out is based upon last used
> time rather than last write time. It can choose to push out pages at
> any time, and it's only every 5 seconds or so the the system task
> (bdflush?) tries to force out all dirty file system pages. NCQ
> exaggerates the situation, but I believe the issue pre-exists NCQ or
> the SCSI equivalent of years past.
Indeed there do seem to be issues with Linux and fsync. Its one of
things I'm trying to get a
handle on as well - the relationship between fsync and flushes of
controller and/or disk caches.
>
> The rest of your email relies on the premise that POSIX enforces such
> a thing, or that systems are POSIX compliant. :-)
>
True. I'm hoping someone (Jignesh?) will be prompted to remember.
It may have been something in a blog related to ZFS vs other
filesystems, but so far I'm coming
up empty in google. doesn't feel like something I imagined though.
James
