software raid

Jérémie j.tarot at
Thu Mar 23 10:12:45 UTC 2006

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

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
    - 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



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