Disk defragmenter in Linux

Jeff Vian jvian10 at charter.net
Fri Dec 30 14:06:42 UTC 2005

On Fri, 2005-12-30 at 11:07 +0800, John Summerfied wrote:
> Jeff Vian wrote:
> > 
> > Exactly, and IIRC the filesystem knows that if it needs X amount of
> > space for a file, then Y number of inodes are marked for use for that
> > file at the beginning.  Thus space allocated is as contiguous as is
> > efficient for read/write on the disk.
> If "the filesystem knows that if it needs X amount of space for a file," 
> that implies there's a way of telling it that.
> How's that done? I don't recall any system call for *x (there is one for 
> OS/2), and one could do it in JCL in IBM's OS in the 60s), but in the *x 
> world I've never seen a way to do it.
I believe many apps know the size of the file being
transferred/copied/extracted and reserve space for it.

I know that several ftp clients know as soon as they start the transfer
exactly how many bytes they should receive.  Several other things
similarly know the expected file size being handled.

It would surprise me if rpm did not know that and be able to reserve
space for the file to be placed as soon as each file begins to be
extracted. Especially since rpm (some versions at least) does a check of
the file it extracts to verify it is intact.
> > 
> -- 
> Cheers
> John
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