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SubjectRe: IDE DMA Problems...system hangs
At 08:28 PM 2/14/2001 +0000, Alan Cox wrote:
> > Anybody else having these problems with a ide raid 5?
> > The Raid 5 performance should also be questioned..here are some number
> > returned by hdparam
>
>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
in the system (4 PCI and 1 onboard AUS a7v mobo). This gives me the
ability to have 10 master drives. Since I am only striping on one drive per
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?


> > Feb 13 05:23:27 bertha kernel: hdo: dma_intr: status=0x51 { DriveReady
> > SeekComplete Error }
> > Feb 13 05:23:27 bertha kernel: hdo: dma_intr: error=0x84 {
> DriveStatusError
> > BadCRC }
>
>You have inadequate cabling. CRC errors are indications of that. Make sure you
>are using sufficiently short cables for ATA33 and proper 80pin ATA66 cables.

All the cables are ATA/100 capable. But I cannot think of another reason
as to why I might be getting CRC errors. I will invest in better cables
and see if it changes anything.

> > Feb 13 12:12:42 bertha kernel: hdg: irq timeout: status=0x50 { DriveReady
> > SeekComplete }
> > Feb 13 12:13:02 bertha kernel: hdg: timeout waiting for DMA
>
>This could be cabling too, cant be sure
>
> > Feb 13 12:13:12 bertha kernel: hdg: DMA disabled
>
>It gave up using DMA

agreed.


> > Feb 13 12:13:12 bertha kernel: ide3: reset: success <------- * SYSTEM
> HUNG
> > AT THIS POINT *
>
>Ok thats a reasonable behaviour, except it shouldnt have then hung.

This is also my main point of frustration. The system should be able to
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.

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

J.Sidhu






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