Solaris Volume Manager Administration Guide

Maintaining RAID 1 Volumes

Solaris Volume Manager reports status information on RAID 1 volumes and submirrors so a system administrator can determine what, if any, maintenance action is required. The following table explains mirror states.

Table 10–1 Submirror States


State	Meaning
Okay	The submirror has no errors and is functioning correctly.
Resyncing	The submirror is actively being resynchronized. An error has occurred and been corrected, the submirror has just been brought back online, or a new submirror has been added.
Needs Maintenance	A slice (or slices) in the submirror has encountered an I/O error or an open error. All reads and writes to and from this slice in the submirror have been discontinued.

Additionally, for each slice in a submirror, the metastat command shows the “Device” (device name of the slice in the stripe); “Start Block” on which the slice begins; “Dbase” to show if the slice contains a state database replica; “State” of the slice; and “Hot Spare” to show the slice being used to hot spare a failed slice.

The slice state is perhaps the most important information when you are troubleshooting mirror errors. The submirror state only provides general status information, such as “Okay” or “Needs Maintenance.” If the submirror reports a “Needs Maintenance” state, refer to the slice state. You take a different recovery action if the slice is in the “Maintenance” or “Last Erred” state. If you only have slices in the “Maintenance” state, they can be repaired in any order. If you have a slices in the “Maintenance” state and a slice in the “Last Erred” state, you must fix the slices in the “Maintenance” state first then the “Last Erred” slice. See Overview of Replacing and Enabling Components in RAID 1 and RAID 5 Volumes.

The following table explains the slice states for submirrors and possible actions to take.

Table 10–2 Submirror Slice States


State	Meaning	Action
Okay	The component has no errors and is functioning correctly.	None.
Resyncing	The component is actively being resynchronized. An error has occurred and been corrected, the submirror has just been brought back online, or a new submirror has been added.	If desired, monitor the submirror status until the resynchronization is done.
Maintenance	The component has encountered an I/O error or an open error. All reads and writes to and from this component have been discontinued.	Enable or replace the failed component. See How to Enable a Slice in a Submirror, or How to Replace a Slice in a Submirror. The `metastat` command will show an `invoke` recovery message with the appropriate action to take with the `metareplace` command. You can also use the `metareplace -e` command.
Last Erred	The component has encountered an I/O error or an open error. However, the data is not replicated elsewhere due to another slice failure. I/O is still performed on the slice. If I/O errors result, the mirror I/O will fail.	First, enable or replace components in the “Maintenance” state. See How to Enable a Slice in a Submirror, or How to Replace a Slice in a Submirror. Usually, this error results in some data loss, so validate the mirror after it is fixed. For a file system, use the `fsck` command, then check the data. An application or database must have its own method of validating the device.

How to Check the Status of Mirrors and Submirrors

Use one of the following methods to check mirror or submirror status.

From the Enhanced Storage tool within the Solaris Management Console, open the Volumes node, choose the mirror, then choose Action->Properties. Follow the instructions on screen. For more information, see the online help.

Run the metastat command on a mirror to see the state of each submirror, the pass number, the read option, the write option, and the size of the total number of blocks in mirror. For example, to check the status of the one-way mirror d70, use:

# metastat d70
d70: Mirror
    Submirror 0: d71
      State: Okay         
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 12593637 blocks

d71: Submirror of d70
    State: Okay         
    Size: 12593637 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Reloc  Hot Spare
        c1t3d0s3                   0     No    Okay         Yes    
    Stripe 1:
        Device              Start Block  Dbase State        Reloc  Hot Spare
        c1t3d0s4                   0     No    Okay         Yes    
    Stripe 2:
        Device              Start Block  Dbase State        Reloc  Hot Spare
        c1t3d0s5                   0     No    Okay         Yes

See How to Change RAID 1 Volume Options to change a mirror's pass number, read option, or write option.

See metastat(1M) for more information about checking device status.

Example—Checking Status of RAID 1 Volumes

Here is sample output from the metastat command.

# metastat
d0: Mirror
    Submirror 0: d1
      State: Okay        
    Submirror 1: d2
      State: Okay        
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 5600 blocks
 
d1: Submirror of d0
    State: Okay        
    Size: 5600 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Hot Spare
        c0t2d0s7                   0     No    Okay        
 
...

For each submirror in the mirror, the metastat command shows the state, an “invoke” line if there is an error, the assigned hot spare pool (if any), size in blocks, and information about each slice in the submirror.

How to Change RAID 1 Volume Options

Make sure that you have root privilege and that you have a current backup of all data.

Check Background Information for Changing RAID 1 Volume Options.

Use one of the following methods to change mirror options.
- From the Enhanced Storage tool within the Solaris Management Console, open the Volumes node, choose the mirror, then choose Action->Properties. Follow the instructions on screen. For more information, see the online help.
- Use the metaparam command to display and change a mirror's options. For example, to change a mirror to “first”, rather than round-robin, for reading, use the following:
  # metaparam -r first mirror
  See RAID 1 Volume Options for a description of mirror options. Also see the metaparam(1M) man page.

Example—Changing a RAID 1 Volume's Read Policy

# metaparam -r geometric d30
# metaparam d30
d30: mirror current parameters are:
    Pass: 1
    Read option: geometric (-g)
    Write option: parallel (default)

In this example, the -r option changes a mirror's read policy to geometric.

Example—Changing a RAID 1 Volume's Write Policy

# metaparam -w serial d40
# metaparam d40
d40: mirror current parameters are:
    Pass: 1
    Read option: roundrobin (default)
    Write option: serial (-S)

In this example, the -w option changes a mirror's write policy to serial.

Example—Changing a RAID 1 Volume's Pass Number

# metaparam -p 5 d50
# metaparam d50
d50: mirror current parameters are:
    Pass: 5
    Read option: roundrobin (default)
    Write option: parallel (default)

In this example, the -p option changes a mirror's pass number to 5.

How to Expand a RAID 1 Volume

Make sure that you have root privilege and that you have a current backup of all data.

Read Background Information for RAID 1 Volumes.

Use one of the following methods to expand a mirror.
- From the Enhanced Storage tool within the Solaris Management Console, open the Volumes node, choose the mirror, then choose Action->Properties and click the Components tab. Follow the instructions on screen. For more information, see the online help.
- Use the metattach command to attach additional slices to each submirror. For example, to attach a component to a submirror, use the following:
  # metattach submirror component
  Each submirror in a mirror must be expanded. See the metattach(1M) man page for more information.

Example—Expanding a Two-Way Mirror That Contains a Mounted File System

# metastat
d8: Mirror
    Submirror 0: d9
      State: Okay        
    Submirror 1: d10
      State: Okay        
...
# metattach d9 c0t2d0s5
d9: component is attached
# metattach d10 c0t3d0s5
d10: component is attached

This example shows how to expand a mirrored mounted file system by concatenating two disk drives to the mirror's two submirrors. The mirror is named d8 and contains two submirrors named d9 and d10.

Where to Go From Here

For a UFS, run the growfs(1M) command on the mirror volume. See How to Expand a File System.

An application, such as a database, that uses the raw volume must have its own way of growing the added space.