On Tue, 2007-10-30 at 12:52 +0100, Simon Lundell wrote: > Hi! > That O_DIRECT worked pretty well: > > Discontinuities before: 1445 > Discontinuities after: 398
Better > > That is on a directory that the ordinary 'copy' could not defragment > more. I had a little trouble aligning buffers and writing files whose > length was not a multiple of the required alignment. I didn't think about those limitations when I suggested it, but that is something you need to be careful about. Allocating the buffers with posix_memalign() should take care of the first concern. > Do you think the improvement is JFS-specific or does other > filesystems work in the same way? It may help other file systems. It depends on whether their get_block operation handles multiple-block allocations efficiently. It looks like xfs and ext[234] would behave the same. I'm not sure about reiserfs. > Is it correct that on JFS the ideal number of extents should be 1 for > each file, independent on file size? Up to a point. The maximum size of an extent in jfs is (64 GB - 4 KB), so ideally you could have one extent for every ~64 GB of file data. Shaggy -- David Kleikamp IBM Linux Technology Center ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Jfs-discussion mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/jfs-discussion
