aacraid and extremeley high iowait

[Daniel Rogers]

Hi,

I have a PowerEdge 1800 w/ dual 3.0Ghz Xeon's in 64 bit mode running
CentOS 4.  I have a CERC six channel controller and a 3x80GB RAID-5.
The driver is aacraid and my version is  1.1-5[2412].

When copying large amounts of data onto , iowait becomes extremely high,
to the point where the system stalls and essentially becomes usuable
until the disk activity finishes.

1) Is anyone else experiencing this problem?

2) Are there tunable parameters to help mediate this?

I am aware of /sys/block/sda/queue and /sys/block/sda/queue/iosched but
I don't know what any of the parameters do and I am unwilling to start
mucking around with magic numbers without guidance.  A document
describing these parameters would be helpful too.

-- 
Daniel