RE: On very different journalling activity on 2 servers.

[Stephen DeBrass <debrass staff singnet com sg>]

On Thu, 6 Feb 2003, Nico Morrison wrote:

> Hello,
> 
> I have upgraded the 'bad' machine with the latest 'up2date' kernel, but it
> is possible that GRUB is still loading the older kernel. Our sysadmin at the
> dayacentre says the console shows the old kernel kernel-2.4.7-10 
> 
> This might have happened because the first kernel upgrade I did on this
> machine I did manually by downloading the .rpm & installing it locally.
> 
> Now I know to use /use/sbin/up2date instead but ......

You may need to add an entry to /etc/grub.conf that looks something like:
title Red Hat Linux (2.4.19)
        root (hd0,0)
        kernel /vmlinuz-2.4.19 ro root=/dev/hda7

I believe grub picks defaults to booting the first entry it finds, someone
correct me if I'm wrong, I'm not all too familiar with grub...

> How do I tell from the machine (SSH) which kernel it is actually running?

uname -a

> Thanks - sorry to be so ignorant.

No problem :)

> Regards,
> Nico Morrison
> nico morrison micronicos com
> ___________________________________________
> Micronicos Limited  -  London, UK.
> Tel: +44 20 8870 8849 Fax: +44 20 8870 5290
> ___________________________________________
> 
> From: Stephen C. Tweedie [mailto:sct redhat com]
> Sent: 05 February 2003 10:13
> To: Nico Morrison
> Cc: 'Andrew Morton'; ext3 users list
> Subject: RE: On very different journalling activity on 2 servers.
> 
> 
> Hi,
> 
> On Wed, 2003-02-05 at 08:45, Nico Morrison wrote:
> 
> > [root ns5 nico]# /sbin/hdparm  /dev/hda
> > /dev/hda:
> >  using_dma    =  0 (off)
> 
> > Does this mean that dma is in fact off?
> 
> Yes.
> 
> > Looks like is ON on the server that has no problems and OFF on the one
> with
> > loadsa journalling?
> 
> Yes.
> 
> > What do we need to do & is it safe to turn DMA ON on a busy working public
> > internet server?
> 
> You don't.  
> 
> The trouble is, the kernel usually has a reason for not being in DMA
> mode.  If it can negotiate DMA, it will; but the older of your two
> systems did not do so, so either that older kernel doesn't know how to
> drive the IDE controller in DMA mode safely, or it has detected an error
> on the IDE bus and has backed off to non-DMA mode automatically.  In
> both cases, forcing DMA on manually is not recommended.
> 
> I'd suggest that you upgrade the 7.2 box to the current errata kernel,
> which is the same across all the 7.* releases.  That should give you the
> same updated IDE drivers as the 7.3 box has, and will hopefully get you
> running DMA properly.  If it doesn't, then you're going to have to check
> the logs to see why DMA isn't being negotiated.
> 
> Cheers,
>  Stephen
> 
> 
> 
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