Re: Fragmentation of WAL files

On Thu, 26 Apr 2007, Bill Moran wrote:

> I've seen marketing material that claims that modern NTFS doesn't suffer
> performance problems from fragmentation.

You're only reading half of the marketing material then.  For a balanced
picture, read the stuff generated by the companies that sell defragmenting
tools.  A good one to start with is
http://files.diskeeper.com/pdf/HowFileFragmentationOccursonWindowsXP.pdf

Going back to the Jim's original question, they suggest a Microsoft paper
that talks about how the defrag report can be misleading in respect to
open files.  See http://support.microsoft.com/kb/228198

Also, some of the most interesting details they gloss over are specific to
which version of Windows you're using; the reference guide to the subject
of how NTFS decides how much space to pre-allocate at a time is available
at http://support.microsoft.com/kb/841551 (ZIP file wrapped into EXE,
yuck!)

If you compare them, you can see that the approach they're using in NTFS
has evolved to become more like that used by a good UNIX filesystem over
time.  I think your typical UNIX still has a healthy lead in this area,
but the difference isn't as big as it used to be.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD