Superior disk perf. of 2.4.20-ac (Was: RAID-0 read perf. decreaseafter 2.4.20)

[Mikael Johansson]

Hell Joshua and All!

On Mon, 24 Nov 2003, Joshua Schmidlkofer wrote:

> > >Has anyone else experienced a drastic drop in read performance on
> > >software
> > >RAID-0 with post 2.4.20 kernels? We have a few Athlon XP's here at our

> And this isn't the read-ahead size change thing?

When did this change take place? It would be easy to test then. I did some
more tests on the weekend and found that this isn't RAID related; also
normal single disk access is much faster on the 2.4.20-ac's than on other
recent kernels. Just to summarise, the disk speed on one of the Athlon
XP's (2GHz, 1.5 GB RAM, 2*160 GB Maxtor 6Y080L0) according to bonnie++:

RAID-0		VIA	write	read
2.4.19		none	10,000	  9,000
2.4.20		3.35	73,000	 88,000
2.4.20-ac1	3.35-ac	70,000	135,000
2.4.20-ac2 	3.35-ac	71,000	140,000
2.4.21-pre1     3.35-ac 71,000	 79,000
2.4.21-pre3	3.35-ac 71,000	 79,000
2.4.23-rc3	3.37	65,000	 82,000

single disk
2.4.20-ac2	3.35-ac	55,000	 74,000
2.4.23-rc3	3.37	54,000	 48,000

So the single disk read performance of 2.4.20-ac2 is as fast as a
double RAID-0 array of other kernels.

Have a nice day,
    Mikael J.
    http://www.helsinki.fi/~mpjohans/
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