Re: IDE DMA Problems...system hangs

From: Alan Cox (
Date: Wed Feb 14 2001 - 15:54:26 EST

> >You will get horribly bad performance off raid5 if you have stripes on both
> >hda/hdb or hdc/hdd etc.
> If I am reading this correctly, then by striping on both hda/hdb and
> /hdc/hdd you mean that I have two drives per ide channel. In other words,
> you think I have a Master and a Slave type of a setup? This is
> incorrect. Each drive on the system is a master. I have 5 promise cards

Ok then your performance should be fine (at least reasonably so, the lack
of tagged queueing does hurt)

> ide chanel, the penalty should not be much in terms of performance. Maybe
> its just that the hdparam utility is not a good tool for benchamarking a
> raid set?

Its not a good raid benchmark tool but its a good indication of general problems.
Bonnie is a good tool for accurate assessment.

> disable DMA if its giving it a lot of problems, but it should not hang. I
> have been experiencing this for quite a while with the newer
> kernels. Should I try the latest ac13 patch? I glanced of the changes and
> didnt seem like anything had changed regarding the ide subsystem.

I've not changed anything related to DMA handling specifically. The current
-ac does have a fix for a couple of cases where an IDE reset on the promise
could hang the box dead. That may be the problem.

> Is there anyway I can force the kernel to output more messages...maybe that
> could help narrow down the problem?

Ask He may know the status of the promise support
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This archive was generated by hypermail 2b29 : Thu Feb 15 2001 - 21:00:25 EST