On Sat, 2008-12-13 at 11:40 -0600, Eric Sandeen wrote: > Martin Steigerwald wrote: > > > At the moment it appears to me that disabling write cache may often give > > more performance than using barriers. And this doesn't match my > > expectation of write barriers as a feature that enhances performance. > > Why do you have that expectation? I've never seen barriers advertised > as enhancing performance. :) My initial thoughts were that write barriers would enhance performance, in that, you could have write cache on. So its really more of an expectation that wc+barriers on, performs better than wc+barriers off :) > > I do wonder why barriers on, write cache off is so slow; I'd have > thought the barriers were a no-op. Maybe I'm missing something. > > > Right now a "nowcache" option and having this as default appears to make > > more sense than defaulting to barriers. > > I don't think that turning off write cache is something the filesystem > can do; you have to take that as an administrative step on your block > devices. > > > But I think this needs more > > testing than just those simple high meta data load tests. Anyway I am > > happy cause I have a way to speed up XFS ;-). > > My only hand-wavy concern is whether this has any adverse physical > effect on the drive (no cache == lots more head movement etc?) but then > barriers are constantly flushing/invalidating that cache, so it's > probably a wash. And really, I have no idea. :) > > -Eric > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
