aacraid and extremeley high iowait

[Kris Doosje]

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..

Kris

-----Oorspronkelijk bericht-----
Van: linux-poweredge-bounces at dell.com
[mailto:linux-poweredge-bounces at dell.com]Namens Daniel Rogers
Verzonden: woensdag 14 juni 2006 20:34
Aan: linux-poweredge at dell.com
Onderwerp: aacraid and extremeley high iowait


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

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