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Sunday, July 06, 2008

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Enabling root-on-multipath for SLES9 on zSeries

Change three shell scripts

cd /root ;  cp /sbin/mkinitrd mkinitrd_MPIO

# DEBUG: cp_bin /bin/ls $tmp_mnt/bin
echo -ne "Shared libs:\t"

# ------------ ROOT_ON_MPIO modification: ---------------------------
    # Using module dm-multipath triggers our mods.
    # set a flag, add a feature name and copy commands and
    # config file into initrd.
    if has_module dm-multipath ; then
      ROOT_ON_MPIO=1
      features=(${features[@]} ROOT_ON_MPIO)
      add_module dm-round-robin
      cp_bin $root_dir/sbin/multipath $tmp_mnt/sbin
      cp_bin $root_dir/sbin/dmsetup $tmp_mnt/sbin       #used by vgscan
      cp_bin $root_dir/sbin/mpath_* $tmp_mnt/sbin
      cp_bin $root_dir/sbin/kpartx $tmp_mnt/sbin
      cp_bin $root_dir/sbin/devmap_name $tmp_mnt/sbin   #for udev.rules
      cp -a $root_dir/etc/multipath.conf $tmp_mnt/etc
    fi
# --------------------------------------------------------------------

# ------------ ROOT_ON_MPIO modification: ---------------------------
      if [ -n "$ROOT_ON_MPIO" ] ; then
            cat_linuxrc <<-'EOF'
            |echo "ROOT_ON_MPIO -------------------"
            |multipath -v0
            |sleep 1
            |# Map the partitions of each multipath /dev/mapper device
            |for i in $(ls /dev/mapper); do
            |     if [ $i != "." ] ; then
            |           if [ $i != ".." ] ; then
            |                 if [ $i != "control" ]; then
            |                   echo "... $i "
            |                   kpartx -a -v /dev/mapper/$i
            |                 fi
            |           fi
            |     fi
            |done
            |#  Path events from now to when boot.multipathd runs are lost.
            |echo "done - if root is a partition ignore -unable to find vg mapper- "
            EOF
      fi
# Note: original code assumed root_dm meant only LVM2
# -------------------------------------------------------------------

#ROOT_ON_MPIO: Clean up and/or re-populate the /dev/mapper dir.
# That's essential if using multipath root device since the
# initrd's /dev/mapper directory from ramdisk is gone and
# neither hotplug nor running /sbin/multipath recreate's it on SLES9.
/sbin/dmsetup mknodes

#! /bin/sh
# ------Modified for ROOT_ON_MPIO
returnRC() {
 return $1
 }

savedRC=$?

       # ROOT_ON_MPIO: Map the partitions of each /dev/mapper multipath device.
       # No harm kpartx-ing a partition name.
       # Running script twice will kpartx an LVM vol (if any): not harmful.
       for i in $(ls /dev/mapper); do
          if [ $i != "." ] ; then
            if [ $i != ".." ] ; then
              if [ $i != "control" ]; then
                echo "...  kpartx of /dev/mapper/$i"
                kpartx -av /dev/mapper/$i
              fi
            fi
          fi
       done
       echo
       # trying to preserve PROGRAM's exit code for rc_status
       returnRC $savedRC

Change configuration files

/dev/mapper/lun002p1 /            ext3    acl,user_xattr   1 1
/dev/mapper/lun000p1 /boot        ext3    acl,user_xattr   1 2
/dev/sys/home        /home        ext3    acl,user_xattr   1 2
/dev/sys/opt         /opt         ext3    acl,user_xattr   1 2
/dev/sys/usr         /usr         ext3    acl,user_xattr   1 2
/dev/sys/var         /var         ext3    acl,user_xattr   1 2
/dev/sys/swap1       swap         swap    pri=42           0 0
devpts               /dev/pts     devpts  mode=0620,gid=5  0 0
proc                 /proc        proc    defaults         0 0
sysfs                /sys         sysfs   noauto           0 0

Using a multipath boot partition

multipath -l lunB		Display its SCSI device names; one is sdb (perhaps).
umount /boot; dmsetup remove lunBp1; dmsetup remove lunB
mount /dev/sdb1 /boot		Use an sd? name from multipath -l's response
zipl -V

umount /boot
multipath -v1 lunB; kpartx -av /dev/mapper/lunB
mount /dev/mapper/lunBp1 /boot

Maintenance Issues

Example - Convert a DASD + multipath SCSI system to all-SCSI w/ root-on-multipath-partition

 multipaths {
 multipath {
 wwid 360050768016180762800000000000288
 alias lunA
 }
 multipath {
 wwid 36005076801618076280000000000020d
 alias lunB
 }
}

/dev/mapper/lunAp1   /       ext3   acl,user_xattr   1 1
/dev/mapper/lunBp1   /boot   ext3   acl,user_xattr   1 2
  instead of
/dev/dasda1          /       ext3   acl,user_xattr   1 1
/dev/dasda2          /boot   ext3   acl,user_xattr   1 2

multipath -l lunB		Display its scsi device names; one is sdb (perhaps).
umount /boot; dmsetup remove lunBp1; dmsetup remove lunB
mount /dev/sdb1 /boot		Use an sd? name from multipath -l's response
zipl -V
umount /boot
multipath -v1 lunB; kpartx -av /dev/mapper/lunB
mount /dev/mapper/lunBp1 /boot

reboot