openSolaris 2008 - Removing RAID-1 Volumes (Unmirroring) - Solaris Volume Manager Administration Guide

How to Unmirror a File System

Use this procedure to unmirror a file system that can be unmounted while the system is running. To unmirror root (/), /var, /usr, or swap, or any other file system that cannot be unmounted while the system is running, see How to Unmirror a File System That Cannot Be Unmounted.

Before You Begin

Read Creating and Maintaining RAID-1 Volumes.

Make sure that you have root privilege and that you have a current backup of all data.
Verify that at least one submirror is in the Okay state.
```
# metastat mirror
```
Unmount the file system.
```
# umount /file-system
```
Detach the submirror that will continue to be used for the file system.
```
# metadetach mirror submirror
```
For more information, see the metadetach(1M) man page.
Clear the mirror and remaining subcomponents.
```
# metaclear -r mirror
```
For more information, see the metaclear(1M) man page.
Edit the /etc/vfstab file to use the component detached in Step 4, if necessary.
Remount the file system.
```
# mount /file-system
```

Example 11-21 Unmirroring the /opt File System

# metastat d4
d4: Mirror
    Submirror 0: d2
      State: Okay        
    Submirror 1: d3
      State: Okay        
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 2100735 blocks (1.0 GB)

d2: Submirror of d4
    State: Okay         
    Size: 2100735 blocks (1.0 GB)
    Stripe 0:
        Device     Start Block  Dbase        State Reloc Hot Spare
        c0t0d0s0          0     No            Okay   Yes 


d3: Submirror of d4
    State: Okay         
    Size: 2100735 blocks (1.0 GB)
    Stripe 0:
        Device     Start Block  Dbase        State Reloc Hot Spare
        c1t0d0s0          0     No            Okay   Yes 

...
# umount /opt
# metadetach d4 d2
d4: submirror d2 is detached
# metaclear -r d4
d4: Mirror is cleared
d3: Concat/Stripe is cleared
(Edit the /etc/vfstab file so that the entry for /opt is changed from d4 to the underlying slice or volume)
# mount /opt

In this example, the /opt file system is composed of a two-way mirror, d4. The submirrors of the mirror are d2 and d3. The submirrors are composed of slices /dev/dsk/c0t0d0s0 and /dev/dsk/c1t0d0s0. The metastat command verifies that at least one submirror is in the “Okay” state. (A mirror with no submirrors in the “Okay” state must be repaired first.) The file system is unmounted. Then, submirror d2 is detached. The metaclear -r command deletes the mirror and the other submirror, d3.

Next, the entry for /opt in the /etc/vfstab file is changed to reference the underlying slice.

In this example the /etc/vfstab file contains the following entry for the /opt file system:

/dev/md/dsk/d4  /dev/md/rdsk/d4  /opt ufs  2  yes -

Change the entry to read as follows:

/dev/md/dsk/d2  /dev/md/rdsk/d2  /opt ufs  2  yes -

By using the submirror name, you can continue to have the file system mounted on a volume. Finally, the /opt file system is remounted.

By using d2 instead of d4 in the /etc/vfstab file, you have unmirrored the mirror. Because d2 consists of a single slice, you can mount the file system on the slice name (/dev/dsk/c0t0d0s0) if you do not want the device to support a volume.

How to Unmirror a File System That Cannot Be Unmounted

Use this task to unmirror file systems, including root (/), /usr, /opt, and swap, that cannot be unmounted during normal system operation.

Make sure that you have root privilege and that you have a current backup of all data.
Verify that at least one submirror is in the Okay state.
```
# metastat mirror
```
Detach the submirror that will continue to be used for the file system.
```
# metadetach mirror submirror
```
For more information, see the metadetach(1M) man page.
Use one of the following commands, depending the file system you want to unmirror:
- For the /usr, /opt, or swap file systems, change the file system entry in the /etc/vfstab file to use a non-Solaris Volume Manager device (slice).
- For the root (/) file system only: run the metaroot command.
```
# metaroot rootslice
```
  For more information, see the metaroot(1M) man page.
Reboot the system.
```
# reboot
```
Clear the remaining mirror and submirrors.
```
# metaclear -r mirror
```
For more information, see the metaclear(1M) man page.

Example 11-22 Unmirroring the root (/) File System

# metastat d0
d0: Mirror
    Submirror 0: d10
      State: Okay        
    Submirror 1: d20
      State: Okay        
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 2100735 blocks (1.0 GB)

d10: Submirror of d0
    State: Okay         
    Size: 2100735 blocks (1.0 GB)
    Stripe 0:
        Device     Start Block  Dbase        State Reloc Hot Spare
        c0t3d0s0          0     No            Okay   Yes 


d20: Submirror of d0
    State: Okay         
    Size: 2100735 blocks (1.0 GB)
    Stripe 0:
        Device     Start Block  Dbase        State Reloc Hot Spare
        c1t3d0s0          0     No            Okay   Yes 


# metadetach d0 d20
d0: submirror d20 is detached
# metaroot /dev/dsk/c0t3d0s0
# reboot
...
# metaclear -r d0
d0: Mirror is cleared
d10: Concat/Stripe is cleared
# metaclear d20
d20: Concat/Stripe is cleared

In this example, the root (/) file system is a two-way mirror, d0. The submirrors of the mirror are d10 and d20. The submirrors are composed of slices /dev/dsk/c0t3d0s0 and /dev/dsk/c1t3d0s0. The metastat command verifies that at least one submirror is in the “Okay” state. (A mirror with no submirrors in the “Okay” state must be repaired first.) Submirror d20 is detached to make d0 a one-way mirror.

The rootslice is the slice containing the root (/) file system. The metaroot command is run, using the rootslice from which the system is going to boot. This command edits the /etc/system and /etc/vfstab files. The command removes information that specifies mirroring of the root (/) file system.

After rebooting the system, the metaclear -r command deletes the mirror and the other submirror, d10. The last metaclear command clears submirror d20.

Example 11-23 Unmirroring the swap File System

# metastat d1
d1: Mirror
    Submirror 0: d11
      State: Okay        
    Submirror 1: d21
      State: Okay        
...
# metadetach d1 d21
d1: submirror d21 is detached
(Edit the /etc/vfstab file to change the entry for swap from metadevice to slice name)
# reboot
...
# metaclear -r d1
d1: Mirror is cleared
d11: Concat/Stripe is cleared
# metaclear d21
d21: Concat/stripe is cleared

In this example, the swap file system is made of a two-way mirror, d1. The submirrors of the mirror are d11 and d21. The submirrors are composed of slices /dev/dsk/c0t3d0s1 and /dev/dsk/c1t3d0s1. The metastat command verifies that at least one submirror is in the “Okay” state. (A mirror with no submirrors in the “Okay” state must be repaired first.) Submirror d21 is detached to make d1 a one-way mirror. Next, the /etc/vfstab file is edited to change the entry for swap to reference the slice that is in submirror d21.

In this example, the /etc/vfstab file contains the following entry for the swap file system:

/dev/md/dsk/d4  /dev/md/rdsk/d4  /opt ufs  2  yes -

/dev/md/dsk/d1 - - swap - no -

Change the entry to read as follows:

/dev/dsk/c0t3d0s1 - - swap - no -

After rebooting the system, the metaclear -r command deletes the mirror and the other submirror, d11. The final metaclear command clears submirror d21.