Root (Boot Disc) Mirroring Using Solaris Volume Manager (SVM)

For added fail-safe for our servers, besides having good backups, is having our boot discs mirrored. The following steps were done using Solaris 10 on a sparc machine (V490).

Assumptions:
HDD0 - c0t0d0 (Primary Disc)
HDD1 - c0t1d0

Partitions of HDD0:
/ - c0t0d0s0
swap - c0t0d0s1
backup - c0t0d0s2 (this represents the whole disc)
/var - c0t0d0s3
/opt - c0t0d0s4
unassigned - c0t0d0s7 (this would be used to store our metadbs)

1. Start by making HDD1's partition table the same as HDD0:

# prtvtoc /dev/rdsk/c0t0d0s2 | fmthard -s - /dev/rdsk/c0t1d0s2

2. Create atleast 2 (tough i prefer 3 which i will be using) state databases on each disc.

# metadb -afc 3 c0t0d0s7 c0t1d0s7

whereas:
-a = add state database
-f = force (this is needed for HDD0 which is mounted)
-c # = number of state databases in each slice

3. Initialize each disc.

HDD0
# metainit -f d10 1 1 c0t0d0s0
# metainit -f d11 1 1 c0t0d0s1
# metainit -f d13 1 1 c0t0d0s3
# metainit -f d14 1 1 c0t0d0s4

HDD1
# metainit -f d20 1 1 c0t1d0s0
# metainit -f d21 1 1 c0t1d0s1
# metainit -f d23 1 1 c0t1d0s3
# metainit -f d24 1 1 c0t1d0s4

4. Initialize the mirrors.

# metainit d0 -m d10
# metainit d1 -m d11
# metainit d3 -m d13
# metainit d4 -m d14

5. Metaroot and editing of /etc/vfstab to boot to our mirror.

# cat /etc/vfstab (to check vfstab before metaroot)
#device device mount FS fsck mount mount
#to mount to fsck point type pass at boot options
#
fd - /dev/fd fd - no -
/proc - /proc proc - no -
/dev/dsk/c0t0d0s1 - - swap - no -
/dev/dsk/c0t0d0s0 /dev/rdsk/c0t0d0s0 / ufs 1 no -
/dev/dsk/c0t0d0s3 /dev/rdsk/c0t0d0s3 /var ufs 1 no -
/dev/dsk/c0t0d0s4 /dev/rdsk/c0t0d0s4 /opt ufs 1 no -
/devices - /devices devfs - no -
ctfs - /system/contract ctfs - no -
objfs - /system/object objfs - no -
swap - /tmp tmpfs - yes -

# metaroot d0 (only use this for the root slice)

# cat /etc/vfstab (to check vfstab after metaroot)
#device device mount FS fsck mount mount
#to mount to fsck point type pass at boot options
#
fd - /dev/fd fd - no -
/proc - /proc proc - no -
/dev/dsk/c0t0d0s1 - - swap - no -
/dev/md/dsk/d0 /dev/md/rdsk/d0 / ufs 1 no -
/dev/dsk/c0t0d0s3 /dev/rdsk/c0t0d0s3 /var ufs 1 no -
/dev/dsk/c0t0d0s4 /dev/rdsk/c0t0d0s4 /opt ufs 1 no -
/devices - /devices devfs - no -
ctfs - /system/contract ctfs - no -
objfs - /system/object objfs - no -
swap - /tmp tmpfs - yes -

# vi /etc/vfstab (to edit the vfstab to boot to our mirror)
#device device mount FS fsck mount mount
#to mount to fsck point type pass at boot options
#
fd - /dev/fd fd - no -
/proc - /proc proc - no -
/dev/md/dsk/d1 - - swap - no -
/dev/md/dsk/d0 /dev/md/rdsk/d0 / ufs 1 no -
/dev/md/dsk/d3 /dev/md/rdsk/d3 /var ufs 1 no -
/dev/md/dsk/d4 /dev/md/rdsk/d4 /opt ufs 1 no -
/devices - /devices devfs - no -
ctfs - /system/contract ctfs - no -
objfs - /system/object objfs - no -
swap - /tmp tmpfs - yes -

6. Reboot the system

# lockfs -fa
# shutdown -y -g0 -i6

7. Attach the submirrors to the mirror.

# metattach d0 d20
# metattach d1 d21
# metattach d3 d23
# metattach d4 d24

* to monitor the progress of the syncing process

# while true; do metastat | grep %; sleep 3; clear; done

8. Change the core dump directory

# dumpadm (before changing)
Dump content: kernel pages
Dump device: /dev/dsk/c0t0d0s1 (swap)
Savecore directory: /var/crash/e3500
Savecore enabled: yes
# dumpadm -d swap
Dump content: kernel pages
Dump device: /dev/md/dsk/d1 (swap)
Savecore directory: /var/crash/e250
Savecore enabled: yes

9. Update the boot-device parameter to boot to either HDD0 or HDD1

Check the physical device path of both disc

# ls -l /dev/dsk/c0t?d0s0
lrwxrwxrwx 1 root root 41 Jun 5 16:49 /dev/dsk/c0t0d0s0 -> ../../devices/pci@1f,4000/scsi@3/sd@0,0:a
lrwxrwxrwx 1 root root 41 Jun 5 16:49 /dev/dsk/c0t1d0s0 -> ../../devices/pci@1f,4000/scsi@3/sd@1,0:a

Change the major name (in this case "sd") to disk for the boot-device.
Setting the boot-device can be done on the Solaris or the Open Boot (ok) prompt.

Solaris

# eeprom "nvramrc=devalias mirror /pci@1f,4000/scsi@3/disk@1,0:a"
# eeprom "use-nvramrc?=true"
# eeprom boot-device
boot-device=disk net
# eeprom "boot-device=disk mirror net"

Open Boot (ok) prompt

ok nvalias mirror /pci@1f,4000/scsi@3/disk@1,0:a
ok printenv boot-device
boot-device disk net
ok setenv boot-device disk mirror net

10. Lastly, because of the behavior of SVM (the rule half +1 stae database, so we could boot into the OS) we need to add a parameter on /etc/system

# echo "set md:mirrored_root_flag=1" >> /etc/system

You could also opt to add some tuning parameters that could speedup the process of syncing between drives. This sets the size of the buffer used for resynchronizing RAID 1 volumes (mirrors) as the number of 512-byte blocks in the buffer. Setting larger values can increase resynchronization speed.

# echo "set md_mirror:md_resync_bufsz=1024" >> /etc/system (You could change the default value 1024 from 128 to 2048.)