On Mon, Jun 16, 2008 at 10:56:06PM +0200, Robert Millan wrote: > > No. The bios doesn't now anything about the multipathing. It sees a > > number of identical scsi devices sda[a-d] while Linux multipaths this to > > /dev/mapper/mpath0. > > ... then /dev/mapper/mpath0 doesn't belong in device.map. O.k. So the device map only lists Bios/EFI devices?
> > > If it's just an alias for an existing device, we'll probably have to > > > think this through. > > /dev/mapper/mpath0 is kind of an alias for the underlying paths (e.g. > > /dev/sda[a-d]). So whenever grub wants to access /dev/sd? it should > > access the /dev/mapper/mpathX instead. Does this qualify as an alias? > > There are two ways to find out which /dev/sd? build up the multipath > > device: Looking at the multipath -l output or looking at the dm map > > (like I've implemented it in parted). > > So how is this different from software RAID-1? I think it doesn't differ that much - this is why we could reuse most of the grub-installer code for grub1. The basic poinst is that we need grub to write the MBR onto /dev/mapper/mpathX and that the partitions are /dev/mapper/mapthX-partY instead of /dev/sdaY. This is a bit of a special case but sufficient for the installer. -- Guido
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