At Sun, 22 Aug 2010 17:12:14 -0400 CentOS mailing list centos@centos.org wrote:
Matt wrote:
The only problems with switching after install is:
- 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.
- /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
I am not so sure. Actually, what the above line does is map *Grub's* 'hd0' to the *Linux* *device file* /dev/hda -- the primary master IDE (PATA) disk, which is correct for a machine with 'standard' IDE disks. I expect this is wrong for machines with true SCSI, SATA w/SCSI abstraction (all native SATA drivers use SCSI abstraction) or PATA (IDE) w/SCSI abstraction (newer specialized IDE drivers with SCSI abstraction). I expect this is only used by grub installer (that writes the grub stage one loader into the MBR and then maps the BIOS device to the grub device. The *Grub loader* is only going to be using BIOS I/O calls. Grub's loader file(s) use 'hdN' to access file systems (partitions).
On the systems I have seen where there have never been 'native' IDE disks (eg either SATA with a SATA w/SCSI abstraction or PATA w/SCSI abstraction) the grub device.map has:
(hd0) /dev/sda