downgrade ata udma mode at boot time?

downgrade ata udma mode at boot time?

[dean gaudet]

kernel: linux-2.4.19-pre7-ac4
ide hardware: promise 20268 ... a pair of ultra100/tx2
disks: 4x maxtor 6L080J4 80GB D740X

so far in my searching i've only found the hdparm -X switch for
downgrading the ata udma mode (to give me temporary respite from 80-pin
cables which are too long). is there any way to do this on the kernel boot
line?

the problem i'm having is that md is kicking in early enough doing a
parity reconstruct, and udma100 is more demanding than my cables can
satisfy.  the case this hardware is in won't accomodate anything less than
24"  cables... long term i'll be replacing the case and cables, i was just
looking for a temporary workaround.

if i try "hdparm -X66 /dev/hd[egik]" while the parity reconstruct is in
process, i get various results.  rarely it succeeds on all disks.
sometimes it succeeds on 3 of 4 disks, but fails on one.  sometimes it
locks up after trying to set /dev/hde.  (it may not actually be completely
locked up, but it's not responding to the console.)

as far as i can tell the system needs to be completely inactive for the
hdparm to succeed, and there's no way for me to guarantee this at boot
time because md will start reconstructing right away.

thanks
-dean

Re: downgrade ata udma mode at boot time?

[Marc Wilson]

On Mon, May 13, 2002 at 03:28:56PM -0700, dean gaudet wrote:
> so far in my searching i've only found the hdparm -X switch for
> downgrading the ata udma mode (to give me temporary respite from 80-pin
> cables which are too long). is there any way to do this on the kernel boot
> line?

Even Maxtor should have a utility to control what modes the drives are
allowed to use.  If your box isn't smart enough on its own to limit things
to a safe range, then grab a copy of said utility and lock the drives down
so that they CAN'T be used in UDMA5.  Most of them just require booting
from a floppy....

Not so tough.

-- 
Marc Wilson
msw@cox.net

Re: downgrade ata udma mode at boot time?

[Artur Jasowicz]

I am having problems with building/resyncing RAID as well. Here's what I did
for my two RH 7.2 machines:
In /etc/sysconfig/ I created new file called hdparm.cfg with following
content

-d 0 /dev/hde
-d 0 /dev/hdg
-d 0 /dev/hdi
-d 0 /dev/hdk

In /etc/rc.d/rc.sysinit right before root partition gets remounted r/w
(there may be a better spot for that, suggestions, anyone?) I added the
following:

# adjust hd parameters
if [ -e /etc/sysconfig/hdparm.cfg -a -x /sbin/hdparm ]; then
        action $"Adjusting hdparm:" /sbin/hdparm $(/bin/cat
/etc/sysconfig/hdparm.cfg)
fi

Crude, but works.

Artur