Replacing a failed bootdisk
In the following example, the host has a failed bootdisk (c0t0d0). 
Fortunately, the system is using DiskSuite, with a mirror at c0t1d0. 
The following sequence of steps can be used to restore the system to full redundancy. 
System fails to boot
When the system attempts to boot, it fails to find a valid device as required by the boot-device path at device alias "disk". 
It then attempts to boot from the network:
screen not found.
Can't open input device.
Keyboard not present.  Using ttya for input and output.

Sun Ultra 30 UPA/PCI (UltraSPARC-II 296MHz), No Keyboard
OpenBoot 3.27, 512 MB memory installed, Serial #1234567.
Ethernet address m:4c:4d:dr:3s, Host ID: 808f18b5.



Initializing Memory
Timeout waiting for ARP/RARP packet
Timeout waiting for ARP/RARP packet
Timeout waiting for ARP/RARP packet
...
Boot from mirror
At this point, the administrator realizes that the boot disk has failed, 
and queries the device aliases to find the one corresponding to the disksuite mirror:
ok devalias
sds-mirror               /pci@1f,4000/scsi@3/disk@1,0
sds-root                 /pci@1f,4000/scsi@3/disk@0,0
net                      /pci@1f,4000/network@1,1
disk                     /pci@1f,4000/scsi@3/disk@0,0
cdrom                    /pci@1f,4000/scsi@3/disk@6,0:f
...
The administrator then boots the system from the mirror device "sds-mirror":
ok boot sds-mirror
The system starts booting off of sds-mirror. 
However, because there are only two of the original four state database replicas available, a quorum is not achieved. 
The system requires manual intervention to remove the two failed state database replicas:
Starting with DiskSuite 4.2.1, an optional /etc/system parameter exists which allows DiskSuite to boot with just 50% 
of the state database replicas online. 
For example, if one of the two boot disks were to fail, just two of the four state database replicas would be available. 
Without this /etc/system parameter (or with older versions of DiskSuite), the system would complain of "insufficient state database replicas",
and manual intervention would be required on bootup. To enable the "50% boot" behaviour with DiskSuite 4.2.1, execute the following command:
# echo "set md:mirrored_root_flag=1" >> /etc/system
Boot device: /pci@1f,4000/scsi@3/disk@1,0  File and args: 
SunOS Release 5.8 Version Generic_108528-07 64-bit
Copyright 1983-2001 Sun Microsystems, Inc.  All rights reserved.
WARNING: md: d10: /dev/dsk/c0t0d0s0 needs maintenance
WARNING: forceload of misc/md_trans failed
WARNING: forceload of misc/md_raid failed
WARNING: forceload of misc/md_hotspares failed
configuring IPv4 interfaces: hme0.
Hostname: myhost
metainit: myhost: stale databases

Insufficient metadevice database replicas located.

Use metadb to delete databases which are broken.
Ignore any "Read-only file system" error messages.
Reboot the system when finished to reload the metadevice database.
After reboot, repair any broken database replicas which were deleted.

Type control-d to proceed with normal startup,
(or give root password for system maintenance): ******

single-user privilege assigned to /dev/console.
Entering System Maintenance Mode

Apr 10 15:31:08 su: 'su root' succeeded for root on /dev/console
Sun Microsystems Inc.   SunOS 5.8       Generic February 2000

# metadb -i
        flags           first blk       block count
    M     p             unknown         unknown         /dev/dsk/c0t0d0s5
    M     p             unknown         unknown         /dev/dsk/c0t0d0s6
     a m  p  lu         16              1034            /dev/dsk/c0t1d0s5
     a    p  l          16              1034            /dev/dsk/c0t1d0s6
 o - replica active prior to last mddb configuration change
 u - replica is up to date
 l - locator for this replica was read successfully
 c - replica's location was in /etc/lvm/mddb.cf
 p - replica's location was patched in kernel
 m - replica is master, this is replica selected as input
 W - replica has device write errors
 a - replica is active, commits are occurring to this replica
 M - replica had problem with master blocks
 D - replica had problem with data blocks
 F - replica had format problems
 S - replica is too small to hold current data base
 R - replica had device read errors


# metadb -d c0t0d0s5 c0t0d0s6
metadb: myhost: /etc/lvm/mddb.cf.new: Read-only file system

# metadb -i
        flags           first blk       block count
     a m  p  lu         16              1034            /dev/dsk/c0t1d0s5
     a    p  l          16              1034            /dev/dsk/c0t1d0s6
 o - replica active prior to last mddb configuration change
 u - replica is up to date
 l - locator for this replica was read successfully
 c - replica's location was in /etc/lvm/mddb.cf
 p - replica's location was patched in kernel
 m - replica is master, this is replica selected as input
 W - replica has device write errors
 a - replica is active, commits are occurring to this replica
 M - replica had problem with master blocks
 D - replica had problem with data blocks
 F - replica had format problems
 S - replica is too small to hold current data base
 R - replica had device read errors

# reboot -- sds-mirror

Check extent of failures
Once the reboot is complete, the administrator then logs into the system and checks the status of the DiskSuite metadevices.
Not only have the state database replicas failed, but all of the DiskSuite metadevices previously located on device c0t0d0 need to be replaced. 
Clearly the disk has completely failed.
myhost console login: root
Password:  ******
Oct 11 23:04:08 myhost login: ROOT LOGIN /dev/console
Sun Microsystems Inc.   SunOS 5.8       Generic February 2000

# metastat
d0: Mirror
    Submirror 0: d10
      State: Needs maintenance 
    Submirror 1: d20
      State: Okay         
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 13423200 blocks

d10: Submirror of d0
    State: Needs maintenance 
    Invoke: metareplace d0 c0t0d0s0 
    Size: 13423200 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Hot Spare
        c0t0d0s0                   0     No    Maintenance  


d20: Submirror of d0
    State: Okay         
    Size: 13423200 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Hot Spare
        c0t1d0s0                   0     No    Okay         


d1: Mirror
    Submirror 0: d11
      State: Needs maintenance 
    Submirror 1: d21
      State: Okay         
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 2100000 blocks

d11: Submirror of d1
    State: Needs maintenance 
    Invoke: metareplace d1 c0t0d0s1 
    Size: 2100000 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Hot Spare
        c0t0d0s1                   0     No    Maintenance  


d21: Submirror of d1
    State: Okay         
    Size: 2100000 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Hot Spare
        c0t1d0s1                   0     No    Okay         


d4: Mirror
    Submirror 0: d14
      State: Needs maintenance 
    Submirror 1: d24
      State: Okay         
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 2100000 blocks

d14: Submirror of d4
    State: Needs maintenance 
    Invoke: metareplace d4 c0t0d0s4 
    Size: 2100000 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Hot Spare
        c0t0d0s4                   0     No    Maintenance  


d24: Submirror of d4
    State: Okay         
    Size: 2100000 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Hot Spare
        c0t1d0s4                   0     No    Okay         

Replace failed disk and restore redundancy
The administrator replaces the failed disk with a new disk of the same geometry. 
Depending on the system model, the disk replacement may require that the system be powered down. 
The replacement disk is then partitioned identically to the mirror, and state database replicas are copied onto the replacement disk.
Finally, the metareplace command copies that data from the mirror to the replacement disk, restoring redundancy to the system.
# prtvtoc /dev/rdsk/c0t1d0s2 | fmthard -s - /dev/rdsk/c0t0d0s2
fmthard:  New volume table of contents now in place.

# installboot /usr/platform/sun4u/lib/fs/ufs/bootblk /dev/rdsk/c0t0d0s0

# metadb -f -a /dev/dsk/c0t0d0s5

# metadb -f -a /dev/dsk/c0t0d0s6

# metadb -i
        flags           first blk       block count
     a        u         16              1034            /dev/dsk/c0t0d0s5
     a        u         16              1034            /dev/dsk/c0t0d0s6
     a m  p  luo        16              1034            /dev/dsk/c0t1d0s5
     a    p  luo        16              1034            /dev/dsk/c0t1d0s6
 o - replica active prior to last mddb configuration change
 u - replica is up to date
 l - locator for this replica was read successfully
 c - replica's location was in /etc/lvm/mddb.cf
 p - replica's location was patched in kernel
 m - replica is master, this is replica selected as input
 W - replica has device write errors
 a - replica is active, commits are occurring to this replica
 M - replica had problem with master blocks
 D - replica had problem with data blocks
 F - replica had format problems
 S - replica is too small to hold current data base
 R - replica had device read errors

# metareplace -e d0 c0t0d0s0
d0: device c0t0d0s0 is enabled

# metareplace -e d1 c0t0d0s1
d1: device c0t0d0s1 is enabled

# metareplace -e d4 c0t0d0s4
d4: device c0t0d0s4 is enabled

Once the resync process is complete, operating system redundancy has been restored.