From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lutz Vieweg Subject: Fragmentation / repacker / append-performance Date: Fri, 18 Nov 2005 17:34:49 +0100 Message-ID: <437E02A9.2050107@isg.de> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: reiserfs-list@namesys.com Hans Reiser wrote: > 6% fragmentation is enormous. You very much need the > repacker we have not yet written..... There has been talk about such a feature for a long time - did anybody already write a concept on how to do this? Has an effort been estimated? Is somebody already assigned to that task? It's not too difficult for us to implement de-fragmentation mechanisms on the application level, but if the file system can do it - even better... We're currently considering reiser4 for an application that we know would suffer badly from fragmentation, as it needs to often append small amounts of data (a few bytes to a few kB) to lots of files (6M). Alas, such a task does not seem to be covered by any of the usual benchmarks, so we have to do measurements on our own. Any suggestion for optimal configuration parameters we should use? As of yet, we are using XFS for this task, which is significantly faster for that particular application than reiser3. Alas, XFS/kernel-2.6/SMP is known to be unstable under high load for almost a year now, but since the problem is hard to reproduce and those who only need a file server can live with using just one CPU it does not seem to get fixed anytime soon. Regards, Lutz Vieweg PS: I'm still glad we sponsored the 64bit-port years ago, as we're still using reiser3 on a lot of systems that can really use it - and of course newly bought systems are 64bit architectures... :-)