环境：
Solaris2.X
SDS 4.X
failed bootdisk(c0t0d0
mirror disk(c0t1d0)
系统盘c0t0d0硬件故障失败，但系统有一个用SDS做的镜象盘c0t1d0。
下面是替换和恢复系统的过程：
1 从镜象盘引导系统
系统无法正常引导时，我们可以让系统进入硬件维护状态，使用devalias找到镜象盘：
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
...
然后从镜象盘引导： ok boot sds-mirror
这里有一个问题，我们知道DiskSuite的启动有一个要求，就是它的正常的可用的
配置数据库个数（state database replicas）要占它的总数的50%以上，以我们这
个例子说明，比如系统在原来安装时，在c0t0d0s7和c0t1d0s7这两个slice上各建立
2个database replicas，总共有4个replicas，那么因为c0t0d0盘损坏，所以只剩下
c0t1d0上的2个可用，这仍然不符合大于50%的要求，所以系统启动仍然需要手工
干预，进入单用户，删除失败的2个state database replicas：
Boot device: /pci@1f,4000/scsi@3/disk@1,0 File and args:
SunOS Release 5.8 Version Generic_108528-15 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: app01
metainit: 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
《请注意以上的过程提示，因为未满足state replicas大于50%的条件，系统无法进入
正常的运行状态》
# metadb -i
flags first blk block count
M p unknown unknown /dev/dsk/c0t0d0s7
M p unknown unknown /dev/dsk/c0t0d0s7
a m p lu 16 1034 /dev/dsk/c0t1d0s7
a p l 16 1034 /dev/dsk/c0t1d0s7
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
《c0t0d0s7中的replicas的状态标志是M，表示DiskSuite无法正常访问》
# metadb -d c0t0d0s7
《删除失效的replicas》
# 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
《检查》
# reboot -- sds-mirror
《重启动系统》
2 检查系统状态
进入系统后，要确认坏盘上的metadevices，把需要replace的设备名字记下：
# 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
你需要记下这些信息：
d10 -- c0t0d0s0
d11 -- c0t0d0s1
d14 -- c0t0d0s4
以上3个设备是需要替换的。
3 替换失败的硬盘并恢复DiskSuite的配置
拔掉坏盘插入新盘，并按照镜象盘（c0t1d0）的分区表把新盘format。有1个命令可以
很方便的完成这个动作：
# prtvtoc /dev/rdsk/c0t1d0s2 | fmthard -s - /dev/rdsk/c0t0d0s2
但是别忘了这一步，在新盘上安装引导块：
# installboot /usr/platform/sun4u/lib/fs/ufs/bootblk /dev/rdsk/c0t0d0s0
接着是在新盘上创建2个state database replicas:
# metadb -f -a /dev/dsk/c0t0d0s6
# metadb -i
最后一步，恢复DiskSuite原来的镜象配置：
# 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
这一步做完后，你可以用metastat命令观察，新的镜象开始同步。这个过程可以容易地测试，如果你装了DiskSuite，并做了系统盘的镜象， 在做好备份的前提下，可以按照上述内容测试。
一点补充：
=========================================================
DiskSuite 从版本4.2.1开始支持50%的state database replicas的启动，也就是说我们上面所说的当一个盘损坏时的手工干预的过程可以避免。
这个新的SDS的功能需要在文件/etc/system中加入一个参数：
# echo "set md:mirrored_root_flag=1" >;>; /etc/system
例如: 2个盘做镜象，每个盘各有2个state database replicas，当一个盘坏掉，我们只剩下50%的replicas，那么只要你安装了SDS4.2.1并且/etc/system已经做了设置，系统就可以正常启动。
这个新功能很重要而且非常有用 ，它可以让我们在用SDS做镜象时不用再发愁到底一边放几个replicas是最好的问题。手册上称这个功能叫：
----- "50% boot" behaviour of DiskSuite 4.2.1
===============================================================
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我正在准备VxVM下替换失败系统盘的资料，希望很快和它见面，如果自己不懒的话。
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