On Thu, 15 February 2007 23:59:14 +0100, Juan Piernas Canovas wrote:Actually I am interested in the common case, where the machine is not out of space, or memory, or CPU, but when it is appropriately sized to the workload. Not that I lack interest in corner cases, but the "running flat out" case doesn't reflect case where there's enough hardware, now the o/s needs to use it well.Actually, the version of DualFS for Linux 2.4.19 implements a cleaner. In our case, the cleaner is not really a problem because there is not too much to clean (the meta-data device only contains meta-data blocks which are 5-6% of the file system blocks; you do not have to move data blocks).
That sounds as if you have not hit the "interesting" cases yet. Fun
starts when your device is near-full and you have a write-intensive
workload. In your case, that would be metadata-write-intensive. For
one, this is where write performance of log-structured filesystems
usually goes down the drain. And worse, it is where the cleaner can
run into a deadlock.
Being good where log-structured filesystems usually are horrible is a
challenge. And I'm sure many people are more interested in those
performance number than in the ones you shine at. :)