This is the mirror we will be using

root@solaris:/ # metastat d80
d80: Mirror
Submirror 0: d82
State: Okay
Submirror 1: d81
State: Okay
Pass: 1
Read option: roundrobin (default)
Write option: parallel (default)
Size: 96081792 blocks (45 GB)

d82: Submirror of d80
State: Okay
Size: 96081792 blocks (45 GB)
Stripe 0:
Device Start Block Dbase State Reloc Hot Spare
c1t8d0s4 0 No Okay Yes

d81: Submirror of d80
State: Okay
Size: 96081792 blocks (45 GB)
Stripe 0:
Device Start Block Dbase State Reloc Hot Spare
c0t10d0s4 0 No Okay Yes

Device Relocation Information:
Device Reloc Device ID
c1t8d0 Yes id1,sd@TSEAGATE_ST314670LSUN146G3KS2ZHD2
c0t10d0 Yes id1,sd@TSEAGATE_ST314670LSUN146G3KS2RP29

Creating a soft partition and instead of indicating a partition, declare the mirror

root@solaris:/ # metainit d83 -p d80 2g
d83: Soft Partition is setup

Create the filesystem

root@solaris:/ # newfs /dev/md/rdsk/d83
newfs: construct a new file system /dev/md/rdsk/d83: (y/n)? y
Warning: 18560 sector(s) in last cylinder unallocated
/dev/md/rdsk/d83: 4194304 sectors in 207 cylinders of 24 tracks, 848 sectors
2048.0MB in 42 cyl groups (5 c/g, 49.69MB/g, 12032 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
32, 102640, 205248, 307856, 410464, 513072, 615680, 718288, 820896, 923504,
3256352, 3358960, 3461568, 3564176, 3666784, 3769392, 3872000, 3974608,
4077216, 4179824

Check status

root@solaris:/ # metastat -c
d83 p 2.0GB d80
d80 m 45GB d82 d81
d82 s 45GB c1t8d0s4
d81 s 45GB c0t10d0s4
d50 m 516MB d52 d51
d52 s 516MB c1t8d0s7
d51 s 516MB c0t10d0s7
d40 m 19GB d42 d41
d42 s 19GB c1t8d0s6
d41 s 19GB c0t10d0s6
d30 m 19GB d32 d31
d32 s 19GB c1t8d0s5
d31 s 19GB c0t10d0s5
d20 m 31GB d22 d21
d22 s 31GB c1t8d0s1
d21 s 31GB c0t10d0s1
d10 m 19GB d12 d11
d12 s 19GB c1t8d0s0
d11 s 19GB c0t10d0s0

• Solaris