Re: Performance issue with 2.6 md raid0

[Nick Piggin]

Mattias Wadenstein wrote:

> On Fri, 6 Feb 2004, Nick Piggin wrote:
>
>
> > Mattias Wadenstein wrote:
> >
> >
> > > Greetings.
> > >
> > > While testing a file server to store a couple of TB in resonably large
> > > files (>1G), I noticed an odd performance behaviour with the md raid0 in a
> > > pristine 2.6.2 kernel as compared to a 2.4.24 kernel.
> > >
> > > When striping two md raid5:s, instead of going from about 160-200MB/s for
> > > a single raid5 to 300M/s for the raid0 in 2.4.24, the 2.6.2 kernel gave
> > > 135M/s in single stream read performance.
> > Can you try booting with elevator=deadline please?
>
> Ok, then I get 253267 kB/s write and 153187 kB/s read from the raid0. A
> bit better, but still nowhere near the 2.4.24 numbers.
>
> For a single raid5, 158028 kB/s write and 162944 kB/s read.

Any idea what is holding back performance? Is it IO or CPU bound?
Can you get a profile of each kernel while doing a read please?

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