software raid

[Jérémie]

Hi Carl,

I've spent quite some time on this questions, done much googling, and
made boot tests with both lilo and grub... here's what came out of those
experiments

Note: this was under Debian as it is still my OS of choice for
servers... may be Dapper will change this ;)

1) 1 device/1 PCI channel, all masters, _don't_ mess with this, PCI IDE
cards are really cheap !

2) Partitionning: I do LVM on RAID the following way:
    - /boot: RAID1, each partition have the bootable flag set
    - SWAP: RAID1
    - The rest is LVM logical volumes above RAID1 or RAID5 array(s):
      /, /usr,
      /usr/local, /opt,
      /var, /var/log, /tmp,
      /home, /srv
    - All disks have exactly the same partition table, so on configs
with more than 2 disks, I add spare partitions to /boot and swap arrays.
Further, this leverage sfdisk power for initial partitionning of new
disks...
    - Note that, AFAIC, a question remain at this point. I couldn't yet
figure what is the best strategy between creating one global VG or
several one... any insight or experience about this warmly appreciated :)
    - All this is initially done with partman in the d-i without
trouble... just a warning at some point saying that the partition table
has changed (during LVM setup), but you can safely ignore, this seems to
be a d-i bug)

3) Installing bootloader
   a) With LiLo:
     - you have to install it with the d-i, on /dev/md0 in my setup,
when asked if you want to activate it, say no, process ends with an
error... ignore
     - switch to VC2, edit /target/etc/lilo.conf, check that
boot=/dev/md0 add add raid-extra-boot=mbr-only just after, save it
     - chroot /target; lilo -v
     - ctrl+d to get out of chroot
   b) With GRUB:
     - install GRUB with the d-i on /dev/md0
     - switch to VC2
     - On a RAID1 setup with master disks on prim and sec IDE channels:
       # grub
       > device hd(0) /dev/hda
       > root hd(0,0)
       > setup hd(0)
       > device hd(0) /dev/hdc
       > root hd(0,0)
       > setup hd(0)
       > quit

Thanks for your comments

Bests

Jé