> > Yes they were. XFS had barrier support added in 2.6.15. > The XFS was running over a software RAID0 or software RAID5 depending on the product. In both case, my understanding is that either software RAID0 or software RAID5 did not support barrier in 2.6.18. > Yes, that would have been me that said that. I started seeing lots > of boy-racer "tweak your filesystem to go faster" blogs recommending > that unwritten extents should be turned off high up in google > results, with numbers to prove that it improved performance. > > There were two common things wrong with these blogs: > > 1. None of them mentioned that turning off unwritten extents > exposes stale data to users. i.e. a whopping great big > security hole. > > 2. they reported significant performance improvements for > workloads that *didn't use unwritten extents* when they set > this flag. i.e. they mistook run-to-run variablity of the > benchmark for a performance improvement. i.e. Benchmarking > 101 Fail. > > When you get people who do not understand what they are doing and > giving bad advice as the first 10 hits for a google search about > optimising/tuning XFS filesystems, it's a major concern, and so I > took steps to ensure you can't turn off unwritten extents with > mkfs... Thanks for the explanation. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
