RHEL4 - Boot hangs

[Chet Nichols III]

howdy!

> sda: asking for cache data failed
> sda: assuming drive cache: write through
> sdb: asking for cache data failed
> sdb: assuming drive cache: write through
from my previous understanding, this shouldn't cause a boot failure. all
that's happening is the kernel is asking the RAID card for cache parameters
to determine if it should use write-back or write-through.

in write-back, the RAID controller will respond saying that data has been
written/committed to disk before it has actually happened, in write-through,
the RAID controller wont say data has been committed until it has actually
been committed.

in most cases, write-back caching is faster, because there's going to be
less IO wait time (since the RAID controller will respond much quicker with
a confirmation), at which the RAID card will take care of getting stuff
actually committed to disk on its own time. however, you also run the risk
of losing data if you lose power. some people have battery backups on the
controller (i think the battery is on the controller) so if they lose power,
the cache doesnt get lost, and on reboot, whatever is in the cache will get
committed ..not sure if you have that or not.

hopefully that kind of explains why those messages you're seeing wouldn't be
a reason for failure to boot.

you said you tried booting from a previous kernel? was it the same previous
kernel you used before the update? any special modules that were included in
the previous one that would need to be added to the new one?

good luck!

chet

On Tue, May 20, 2008 at 10:15 PM, Sanjay Chakraborty <
sanjaychakrab at gmail.com> wrote:

> Go to rescue mode and run file system check (fsck by unmounting that
> partition first). Some driver might have override something. Can also run
> hdparm also. Update the firemware might help.
>
> On Tue, May 20, 2008 at 1:27 AM, Davis, Jared S. <DavisJar at missouri.edu>
> wrote:
>
> > I'm having trouble booting our web server running RHEL4.  I just recently
> > updated to the 2.6.9-67.0.7 kernel.  We rebooted the machine to do some
> > backup maintenance, and now it hangs at starting 'udev'.  I also get the
> > following message before that (after the booting to kernel message):
> >
> > sda: asking for cache data failed
> > sda: assuming drive cache: write through
> > sdb: asking for cache data failed
> > sdb: assuming drive cache: write through
> >
> > I'm not sure if this has anything to do with the problem or not.  We have
> a
> > RAID set up with 2 LVs.  I also tried booting to a previous version via
> grub
> > with no luck.  Any ideas?
> >
> > Thanks,
> >
> > jared davis.
> >
> >
> >
> > --
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>
>
>
> --
> Regards.
> Sanjay Chakraborty
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-- 
/*
Chet Nichols III
mail: chet.nichols at gmail.com
(aim: chet / twitter: chet)
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