Disk optimization for multithreaded app.

#11

On 2/11/2010 11:30 PM, robertwessel2 (AT) yahoo (DOT) com wrote:

Quote:

On Feb 11, 5:34 pm, Bill Todd<billt... (AT) metrocast (DOT) net> wrote:
Thanks - what you describe above I once knew as the supported way to
accomplish preallocation (which I don't think originally existed in NT)
but had forgotten (at least in any detail - that's why I alluded to it
only vaguely above). Now I feel lazy for not having taken the time to
rediscover it.

Well SetEndOfFile dates back to NT3.1, and the documentation (I
actually have a copy of the Win32 API hardcopy doc from that era) is
similar to the current versions. SetFileValidData is definitely newer
than that, though.

Interestingly, both the old and new versions describe the data in the
extended area as being undefined.

My distinct impression is that the ability to preallocate (using
documented functions) *without* zeroing out the preallocated area
appeared at some point during the past decade - but I obviously could be
mistaken about that. It might have been related to the appearance of
high-water marking if that wasn't present in the earliest versions
(though something similar existed in VMS back in the '80s, so the
technology was hardly new).

- bill

#12

Quote:

mistaken about that. It might have been related to the appearance of
high-water marking if that wasn't present in the earliest versions

NTFS was always supporting ValidDataLength _on disk_.

All Windows's FSDs support this _in memory (as an FCB field)_, but on-disk support is NTFS-only.

Sorry to forget this seek+SetEndOfFile sequence. I was only thinking about ZwCreateFile with AllocationSize.

--
Maxim S. Shatskih
Windows DDK MVP
maxim (AT) storagecraft (DOT) com
http://www.storagecraft.com

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Disk optimization for multithreaded app.

Storage systems Storage system issues, both hardware and software (comp.arch.storage)

Re: Disk optimization for multithreaded app. - 02-12-2010 , 02:05 PM

Re: Disk optimization for multithreaded app. - 02-12-2010 , 03:38 PM