Re: NTFS fragmentation

[Vladimir Dergachev <vdergachev at rcgardis dot com>]

Hi Gary and Larry, 

      Thank you for your comments, replies below:

On Wednesday 02 August 2006 7:08 pm, you wrote:
> >         Any suggestions and comments would be greatly
> > appreciated.
> > Please CC me - I am not on the list.
> >
> >                            thank you very much
> >
> >                                         Vladimir Dergachev
>
> I'll try your test case when I get a chance, but my WAG is that you're
> seeing the effects of Cygwin's creation of sparse files by default for any
> file beyond a certain size.  I unfortunately do not recall what that size
> is.  What happens as you change FILE_SIZE and/or BUFFER_SIZE in your
> script, to maybe a small multiple of your cluster size?

I tried buffer_size of 10K, 100K, 1M and 10M - no big difference, except a 
small decrease in number of fragments for 10M value - could be noise..

I also tried a smaller file size - 3M, the number of fragments decreased to 
33, roughly proportionally to size.

Unfortunately, I do not know what cluster size is.

With regard to sparse files the intent here is to open a file, write data to 
it and the close. No seeks involved, much less void regions. I do understand 
that internally cygwin could do something different. 

I have not found a utility to identify a sparse file yet - if you happen to 
have a link I would greatly appreciate it.

Also, I tried the following experiment - found a 17 MB file in ibiblio.org and 
downloaded it with FireFox. The file ended up fragmented into more than 200 
pieces. Tried the same file with IE - no fragmentation.

It could be, of course, that Firefox is compiled with cygwin, but I have not 
found cygwin.dll anywhere in its installation directory.

                             thank you

                                    Vladimir Dergachev

PS I'll try writing a C program when time permits - any suggestions on what 
API besides regular open/write/close to use ?


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