Readahead with softraid1

[Erik Slagter <erik@slagter.name>]

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Hi,

I am using softraid 1 on two sata disks and I'm trying to get the best
possible performance. IMHO read actions (if properly addressed) should
be split over the two drivers and performed independently. However, I
don't notice anything to back this up. The read performance (with the
dreaded hdparm) shows read performance on sda,sdb and md0 exactly the
same.

I've been playing a bit with readahead and it does matter a bit in that
if I disable readahead for sda/sdb completely, the read rate for these
goes completely down (to be expected) whilst the read rate on md0 stays
the same (also a bit to be expected). Other combinations do not show any
significant impact.

I also played with the i/o scheduler and nr_requests (as from previous
messages here).

What am I doing wrong here???

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