Re: software raid does not do parallel reads under 2.4?

[<pcg@goof.com ( Marc) (A.) (Lehmann )>]

On Fri, Aug 24, 2001 at 08:25:29PM +1000, Neil Brown <neilb@cse.unsw.edu.au> wrote:
> For raid0, the md driver just redirects requests to the right drive.
> It doesn't explicitly serialise or parallelise anything. 2.4 works in
> exactly the same was as 2.2.

then why is 2.2 so much faster?

> With a 2MB chunksize, I would expect a linear read to touch just one
> drive at a time.

why? i read 8mb cvhunks a time (see the dd) so it should read 3x2mb
chunks easily. anyway, i get the same throughput with 64k, 16k etc..
chunksize.

> With a 4K chunk size, I suspect that an linear read would read from
> all the drives in parallel.

maybe, but it's still exactly as fast: 30mb/s, which is slower than one drive
can do.

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