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?
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