aacraid and extremeley high iowait

[r levins]

I also have similar problem with similar setup. I have CERC 1.5 / 6 ch raid 
controller and it performs very poorly. Other than io waits the capacity 
itself of this controller is poor. I am able to achieve at the most 100 
MB/second and that too with RAID 0.

>From: "Stephen John Smoogen" <smooge at gmail.com>
>CC: "linux-poweredge at dell.com" <linux-poweredge at dell.com>
>Subject: Re: aacraid and extremeley high iowait
>Date: Thu, 15 Jun 2006 12:14:38 -0600
>
>On 6/15/06, Kris Doosje <k.doosje at nido.nl> wrote:
> > I have the same problem on a PowerEdge 1800. I'm running Red Hat 
>Enterprise AS 3 on the machine. In the machine are 6 SATA disks (80GB). Two 
>raid arrays are configured: 2 disks in a RAID1, and 4 disks in a RAID1+0. 
>When I read or write a large amount of data, IOwait reaches values around 
>100% and the system becomes very, very slow.
> >
> > Because of this, the machine is almost not used at the moment, which is 
>a shame because it should be a very powerfull machine! Hopefully there's a 
>solution to this problem..
> >
>
>I have talked to techs who have seen these issues with aacraid
>controllers. Some got acceptable performance with a BIOS updates to
>the system. The others just went with other hardware controllers and
>swore never to touch an aac again. The problems seemed to not be with
>the driver but with the controller itself under certain loads (they
>could simulate the same large waits with windows).
>
>
>--
>Stephen J Smoogen.
>CSIRT/Linux System Administrator
>
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