Solaris x86 root filesystem mirroring

Preamble
This document is directed to give idea how to create mirroring of root filesystem in Solaris x86 with the help of Solaris Volume Manager. Here will be used already installed OS and all the work will be done without need of reinstall

Prerequisites
1. First we should be sure have two identical harddisks in the server

# format
 Searching for disks...done
 AVAILABLE DISK SELECTIONS:
       0. c0d0 <DEFAULT cyl 1563 alt 2 hd 255 sec 63>
          /pci@0,0/pci-ide@7,1/ide@0/cmdk@0,0
       1. c0d1 <DEFAULT cyl 1563 alt 2 hd 255 sec 63>
          /pci@0,0/pci-ide@7,1/ide@0/cmdk@1,0
 Specify disk (enter its number): ^C


2. Its need to create small slice for metadb information (usually slice 7) like:

   partition> p
 Current partition table (unnamed):
 Total disk cylinders available: 1563 + 2 (reserved cylinders)

 Part      Tag    Flag     Cylinders        Size            Blocks
   0       root    wm     518 - 1562        8.01GB    (1045/0/0) 16787925
   1       swap    wu       3 -  133        1.00GB    (131/0/0)   2104515
   2     backup    wm       0 - 1562       11.97GB    (1563/0/0) 25109595
   3 unassigned    wm       0               0         (0/0/0)           0
   4 unassigned    wm       0               0         (0/0/0)           0
   5 unassigned    wm       0               0         (0/0/0)           0
   6 unassigned    wm       0               0         (0/0/0)           0
   7 unassigned    wm     134 -  135       15.69MB    (2/0/0)       32130
   8       boot    wu       0 -    0        7.84MB    (1/0/0)       16065
   9 alternates    wu       1 -    2       15.69MB    (2/0/0)       32130

3. Next step is to create the same partitions on the second disk. To avoid human error it is much better to use some kind of automations:

 prtvtoc /dev/rdsk/c0d0s2 > /tmp/c0d0s2.toc
 fmthard -s /tmp/c0d0s2.toc /dev/rdsk/c0d1s2

4. Then we should identify the partitions need to be mirrored:

 # egrep "ufs|swap" /etc/vfstab|grep "/dev/dsk"
 /dev/dsk/c0d0s1 -       -       swap    -       no      -
 /dev/dsk/c0d0s0 /dev/rdsk/c0d0s0        /       ufs     1       no      -


LVM
1. Let’s create few copies of metadb on the partitions we create for this puspose:

 # metadb -a -f -c 2 c0d0s7 c0d1s7

2. It’s time to put our disks where OS reside under management of SVM

 # metainit -f d10 1 1 c0d0s0
 d10: Concat/Stripe is setup
 # metainit -f d11 1 1 c0d0s1
 d11: Concat/Stripe is setup
 # metainit d0 -m d10
 d0: Mirror is setup
 # metainit d1 -m d11
 d1: Mirror is setup
 # metaroot d0

3. Check newly created devices:

 # ls -l /dev/md/rdsk
 total 8
 lrwxrwxrwx   1 root     root          36 Aug 30 18:29 d0 -> ../../../devices/pseudo/md@0:0,0,raw
 lrwxrwxrwx   1 root     root          36 Aug 30 18:29 d1 -> ../../../devices/pseudo/md@0:0,1,raw
 lrwxrwxrwx   1 root     root          37 Aug 30 18:28 d10 -> ../../../devices/pseudo/md@0:0,10,raw
 lrwxrwxrwx   1 root     root          37 Aug 30 18:28 d11 -> ../../../devices/pseudo/md@0:0,11,raw
 # ls -l /dev/md/dsk
 total 8
 lrwxrwxrwx   1 root     root          36 Aug 30 18:29 d0 -> ../../../devices/pseudo/md@0:0,0,blk
 lrwxrwxrwx   1 root     root          36 Aug 30 18:29 d1 -> ../../../devices/pseudo/md@0:0,1,blk
 lrwxrwxrwx   1 root     root          37 Aug 30 18:28 d10 -> ../../../devices/pseudo/md@0:0,10,blk
 lrwxrwxrwx   1 root     root          37 Aug 30 18:28 d11 -> ../../../devices/pseudo/md@0:0,11,blk

4. Make appropriate changes in /etc/vfstab to get boot from mirror, not standard disks

 # egrep "ufs|swap" /etc/vfstab|grep "/dev/md/dsk"
 /dev/md/dsk/d1  -       -       swap    -       no      -
 /dev/md/dsk/d0  /dev/md/rdsk/d0 /       ufs     1       no      -
 
5. The next step is to flush cache buffers and reboot

 # sync;sync;sync
 # init 6

6. It is time to put second disk under management of SVN

 # metainit -f d20 1 1 c0d1s0
 d20: Concat/Stripe is setup
 # metainit -f d21 1 1 c0d1s1
 d21: Concat/Stripe is setup

7. And to add them to created previously mirrors. Be aware process of synchronisation will continue in  background and you can check the process

 # metattach d0 d20
 d0: submirror d20 is attached
 # metattach d1 d21
 d1: submirror d21 is attached

8. Check the process of building mirrors and wait till they finnish

 # metastat
 d1: Mirror
     Submirror 0: d11
       State: Okay
     Submirror 1: d21
       State: Resyncing
     Resync in progress: 96 % done
     Pass: 1
     Read option: roundrobin (default)
     Write option: parallel (default)
     Size: 2104515 blocks (1.0 GB)

 d11: Submirror of d1
     State: Okay
     Size: 2104515 blocks (1.0 GB)
     Stripe 0:
         Device   Start Block  Dbase        State Reloc Hot Spare
         c0d0s1          0     No            Okay   Yes


 d21: Submirror of d1
     State: Resyncing
     Size: 2104515 blocks (1.0 GB)
     Stripe 0:
         Device   Start Block  Dbase        State Reloc Hot Spare
         c0d1s1          0     No            Okay   Yes


 d0: Mirror
     Submirror 0: d10
       State: Okay
     Submirror 1: d20
       State: Resyncing
     Resync in progress: 13 % done
     Pass: 1
     Read option: roundrobin (default)
     Write option: parallel (default)
     Size: 16787925 blocks (8.0 GB)

 d10: Submirror of d0
     State: Okay
     Size: 16787925 blocks (8.0 GB)
     Stripe 0:
         Device   Start Block  Dbase        State Reloc Hot Spare
         c0d0s0          0     No            Okay   Yes


 d20: Submirror of d0
     State: Resyncing
     Size: 16787925 blocks (8.0 GB)
     Stripe 0:
         Device   Start Block  Dbase        State Reloc Hot Spare
         c0d1s0          0     No            Okay   Yes


 Device Relocation Information:
 Device   Reloc  Device ID
 c0d1   Yes      id1,cmdk@AVMware_Virtual_IDE_Hard_Drive=01000000000000000001
 c0d0   Yes      id1,cmdk@AVMware_Virtual_IDE_Hard_Drive=00000000000000000001


Boot

1. Next step is to check if partition on second disk is active

 # fdisk /dev/rdsk/c0d1p0
             Total disk size is 1566 cylinders
             Cylinder size is 16065 (512 byte) blocks

                                               Cylinders
      Partition   Status    Type          Start   End   Length    %
      =         =   =      =
          1       Active    Solaris2          1  1565    1565    100



2. And to add boot record to the second disk to make it bootable

 # /sbin/installgrub /boot/grub/stage1 /boot/grub/stage2 /dev/rdsk/c0d1s0
 stage1 written to partition 0 sector 0 (abs 16065)
 stage2 written to partition 0, 233 sectors starting at 50 (abs 16115)

3. Add new item in the boot menu (/boot/grub/menu.lst) to have alternative way to boot

 title Alternate boot
 root (hd1,0,a)
 kernel /platform/i86pc/multiboot
 module /platform/i86pc/boot_archive

4. Check if the new item is added to the boot menu

 # bootadm list-menu
 The location for the active GRUB menu is: /boot/grub/menu.lst
 default 0
 timeout 10
 0 Solaris 10 5/08 s10x_u5wos_10 X86
 1 Solaris failsafe
 2 Alternate boot

5. That’s all, you have already mirrored root partition (plus swap)

Conclusion
In the document are not mentioned all the options and possibilities of SVM, but only short set, need to done the work. For further information, please consult official Oracle documentation.