On Tue, 2005-11-01 at 18:49 +0000, Peter Grandi wrote: > Hi, I have recently (six weeks ago) switched all the filesystems > on my PC from 'ext3' to JFS for various reasons, in part because > I like the JFS design, in part because I had discovered that > over the past several months my 'ext3' ''root'' filesystem > performance had degraded by 7 times over that of a freshly > loaded copy of itself. > > So I have decided to compare the read speed of my ''root'' JFS > filesystem as it is now, after six weeks of in-place package > upgrades, and how it would be if I reloaded it.
Great. I have never had this kind of data. > I have an otherwise quiescent disc, and I copied my ''root'' > filesystem to it first as a partition image, to preserve the > ''used'' layout, and then by 'tar', so that it would be reloaded > in an optimal ''new'' layout. The filesystem contains around > 7.5GiB of data in 360k files, and 2.3GiB are free. > > The result is that a whole-filesystem 'tar c' on the ''new'' > layout takes 10min., on the ''used'' layout takes 26min., which > is a factor of over 2.5 times longer. I have also done some spot > checks on some largish files that I know have been regularly > updated/rewritten, and there are similar slowdowns (no slowdown > on files that have not been updated in the past six weeks). > > Details here: http://WWW.sabi.co.UK/Notes/anno05-4th.html#051101 This makes a great case for implementing a defragmenter. I'd put it off in the past for a few reasons. 1) there were always more urgent things that needed to be done, 2) the defrag tool that ran on OS/2 was very limited in what it did, and I didn't think that porting it alone would be sufficient, 3) I didn't have any data to demonstrate that fragmentation was a problem. (I noticed the comment about sync adding 4 minutes due to the modified atimes. Have you considered mounting with the noatime option?) > Now 2.5 times is a lot better than 7 times (but the latter was > over a rather longer period on a filesystem with less free space), > but it is still somewhat disappointing, as the average transfer > rate for reading the whole filesystem goes down (on a disc > capable of around 35MiB/s sustained in optimal single-large-file > conditions) from 12MiB/s, which is reasonable, to 5MiB/s, which > is not awesome. Agreed. I still don't anticipate having the time to work on a defragmenter in the near future. This would be a good project from someone wanting to contribute something to jfs. I'd be happy to help. -- David Kleikamp IBM Linux Technology Center ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ Jfs-discussion mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/jfs-discussion
