[CentOS] Kernel Errors Present

Sat Jan 15 12:57:16 UTC 2011
Keith Roberts <keith at karsites.net>

On Sat, 15 Jan 2011, Leonard den Ottolander wrote:

> To: CentOS mailing list <centos at centos.org>
> From: Leonard den Ottolander <leonard at den.ottolander.nl>
> Subject: Re: [CentOS] Kernel Errors Present
> Hi Keith,
> On Thu, 2011-01-13 at 19:03 +0000, Keith Roberts wrote:
>> Well it seems likely it's because the drive is on a
>> 40-wire cable. But the kernel wants to do UDMA at 100 MB/s.
> See hdparm's -X switch to override the (U)DMA mode used for the drive.

Hi Leonard.

Yes, I've added the following into /etc/rc.d/rc.local:

# This script will be executed *after* all the other init 
# You can put your own initialization stuff in here if you 
# want to do the full Sys V style init stuff.

touch /var/lock/subsys/local

# turn off DMA for hde WD drive
# -d0 = off
# -d1 = on
# hdparm -d0 /dev/hde

# hdparm -d1 -Xudma2 /dev/hde
# /dev/hde:
#  setting using_dma to 1 (on)
#  setting xfermode to 66 (UltraDMA mode2)
#  using_dma    =  1 (on)
# set WD drive to use UDMA2 - 33 MB/s
hdparm -d1 -Xudma2 /dev/hde

# set sector count for multiple sector I/O
# WD drives like a low setting
# to prevent I/O data errors.
hdparm -m2 /dev/hde

# enable 32-bit data transfers with a special sync sequence
# required by many chipsets
# /dev/hde:
# setting 32-bit IO_support flag to 3
# IO_support   =  3 (32-bit w/sync)
hdparm -c3 /dev/hde

sleep 10

# end of rc.local

At reset/power on time the IT8212 controller spotted the WD 
drive was on a 40 wire cable, and set the UDMA transfer rate 
to UDMA 2 (33 MB/s).

However for some reason the kernel decided to set the 
transfer rate for the drive to UDMA 5 (100 MB/s).

There were thousands of CRC errors in the SMART data for 
this drive, which would indicate crosstalk problems on the 
40 wire cable being run at too high a speed.

Now I'm using hdparm to reset the drive to UDMA2 (33 MB/s) 
there are no more dma_intr errors occuring, or being 
reported by logwatch.

Thanks for all the feedback on this.

The drive is now working as desired.

I hope to be be getting some custom made 80 wire UDMA IDE 
cables sorted ASAP. That should squeeze extra speed from all 
the drives on the machine.

The 40 wire IDE cables will be packed away safely!

Kind Regards,

Keith Roberts


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