On Wed, 2005-07-13 at 22:50 +0100, David Greaves wrote: > Ming Zhang wrote: > > >On Wed, 2005-07-13 at 22:18 +0100, David Greaves wrote: > > > > > >>Ming Zhang wrote: > >> > >> > >> > >>>>component partitions, e.g. /dev/sda7: 39MB/s > >>>>raid device /dev/md2: 31MB/s > >>>>lvm device /dev/main/media: 53MB/s > >>>> > >>>>(oldish system - but note that lvm device is *much* faster) > >>>> > >>>> > >>>> > >>>> > >>>this is so interesting to see! seems that some read ahead parameters > >>>have negative impact. > >>> > >>> > >>> > >>> > >>I guess each raw device does some readahead, then the md0 does some > >>readahead and then the lvm does some readahead. Theoretically the md0 > >>and lvm should overlap - but I guess that much of the raw device level > >>readahead is discarded. > >> > >>David > >> > >> > >> > >for a streaming read, what you readahead now will always be used exact > >once in near future. at least i think raw device readahead can be turned > >on at the same time with one of OS components, raid or lvm, readahead > >being turned on. but in your case, u get best result when turn only one > >on. > > > >ming > > > > > > > > > > > I doubt it's just me - what results do others get with that script? > > David > my box is in use now. i might try it tomorrow to see what happen. :P Ming - 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
