[CentOS] SDA and HDA

Sun Aug 22 22:35:47 UTC 2010
Robert Heller <heller at deepsoft.com>

At Sun, 22 Aug 2010 17:12:14 -0400 CentOS mailing list <centos at centos.org> wrote:

> 
> 
> Matt wrote:
> >> The only problems with switching after install is:
> >>
> >> 1) you need to be sure the initrd has the (proper) SATA kernel module(s)
> >> in it.  If necessary, you'll have to use mkinitrd to re-create the
> >> initrd file to include the proper driver modules.
> >>
> >> 2) /etc/fstab needs to be fixed, either to use LABEL= (rather than
> >> /dev/hdaN) and your file systems (including swap) need to have file
> >> sytem labels.  (LVM volumes won't be a problem.)
> >>     
> >
> > I changed it in bios to sata mode.  Now after boot up it calls it sda
> > instead of hda and disk I/O is much faster.
> >
> > I see in this file:
> >
> > # cat /boot/grub/device.map
> > # this device map was generated by anaconda
> > (hd0)     /dev/hda
> >
> > Should I change this too sda?  It works and boots the way it is but
> > just wandering?
> >   
> No - I believe grub just refers to hd as hard drive and this does not 
> relate to /dev/sda or /dev/hda

PS: since the OP did not need to 'rewrite' the MBR for any reason, not
changing this was not a problem and I expect won't be unless/until that
needs to be done (eg if/when the disk is ever replaced).

> > Here is fstab:
> >
> > # cat /etc/fstab
> > /dev/VolGroup00/LogVol00 /                       ext3    defaults        1 1
> > LABEL=/boot             /boot                   ext3    defaults        1 2
> > tmpfs                   /dev/shm                tmpfs   defaults        0 0
> > devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
> > sysfs                   /sys                    sysfs   defaults        0 0
> > proc                    /proc                   proc    defaults        0 0
> > /dev/VolGroup00/LogVol01 swap                    swap    defaults        0 0
> >

And the CentOS installer did the 'smart' thing WRT the fstab, and I
expect also in the grub.conf file (eg kernel ...
root=/dev/VolGroup00/LogVol00), making the change from 'legacy' (IDE)
mode to 'native' (SATA) mode painless, so long as the SATA kernel module
was present in the initrd.  Appearently, the installer included this
module, even though the BIOS was faking the disk as an IDE disk.

-- 
Robert Heller             -- 978-544-6933
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