Messages in this thread | | | Date | Wed, 28 May 2008 19:00:29 -0400 | From | Bill Davidsen <> | Subject | Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++) |
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Alan Cox wrote: > On Wed, 28 May 2008 18:34:00 +0200 > "Jens Bäckman" <jens.backman@gmail.com> wrote: > >> On Wed, May 28, 2008 at 10:53 AM, Justin Piszcz <jpiszcz@lucidpixels.com> wrote: >>> Results: >>> >>> http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.html >>> http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.txt >> Either the RAID 1 read speed must be wrong, or something is odd in the >> Linux implementation. There's six drives that can be used for reading >> at the same time, as they contain the very same data. 63MB/s >> sequential looks like what you would get from a single drive. > > Which is fairly typical of a cheap desktop PC where the limitation is the > memory and PCI bridge as much as the drive. > I really don't think that's any part of the issue, the same memory and bridge went 4-5x faster in other read cases. The truth is that the raid-1 performance is really bad, and it's the code causing it AFAIK. If you track the actual io it seems to read one drive at a time, in order, without overlap.
-- Bill Davidsen <davidsen@tmr.com> "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot
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