On Fri, 2006-07-21 at 16:06 -0500, David Masover wrote: > Mike Benoit wrote: > > > Tuning fsync will fix the last wart on Reiser4 as far as benchmarks are > > concerned won't it? Right now Reiser4 looks excellent on the benchmarks > > that don't use fsync often (mongo?), but last I recall the fsync > > performance was so poor it overshadows the rest of the performance. It > > would also probably be more useful to a much wider audience, especially > > if Namesys decides to charge for the repacker. > > If Namesys does decide to charge for the repacker, I'll have to consider > whether it's worth it to pay for it or to use XFS instead. Reiser4 > tends to become much more fragmented than most other Linux FSes -- > purely subjective, but probably true. >
I would like to see some actual data on this. I haven't used Reiser4 for over a year, and when I did it was only to benchmark it. But Reiser4 allocates on flush, so in theory this should decrease fragmentation, not increase it. Due to this I question what you are _really_ seeing, or if perhaps it is a bug in the allocator? Why would XFS or any other multi-purpose file system resist fragmentation noticeably more then Reiser4 does. I don't think the repacker is designed to be a "must have" for every Reiser4 installation. If it was, I would consider Reiser4 to be seriously flawed. Instead I think it is simply designed to improve certain workloads that may cause high fragmentation in hopes of keeping I/O speeds at their peek. Am I correct in this assumption Hans? No Linux file system that I'm aware of has a defragmentor, but they DO become fragmented, just not near as bad as FAT32 used to when MS created their defragmentor. The highest "non-contiguous" percent I've seen with EXT3 is about 12%, FAT32 I have seen over 50%, and NTFS over 30%. In fact I'm running in to a fragmentation issue with ReiserV3 right now that Jeff is working on, but it is more of a worst case scenario issue, not a regular occurrence issue. For "normal" workloads I doubt you would notice much difference at all by using a repacker, 10% maybe? Which is one of the reasons you probably haven't seen a repacker for EXT2/3, even though I'm sure it would improve performance for some people. -- Mike Benoit <[EMAIL PROTECTED]>
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