Chapter 10 RAID 1 (Mirror) Volumes (Tasks)
This chapter explains how to perform Solaris Volume Manager tasks
related to RAID 1 volumes. For information about related concepts, see Chapter 9, RAID 1 (Mirror) Volumes (Overview).
RAID 1 Volumes (Task Map)
The following task map identifies the procedures needed to manage Solaris Volume Manager
RAID 1 volumes.
Creating a RAID 1 Volume
How to Create a RAID 1 Volume From Unused Slices
-
Check Prerequisites for Creating Solaris Volume Manager Elements and Background Information for Creating RAID 1 Volumes.
-
Create two stripes or concatenations, which will be the submirrors.
See How to Create a RAID 0 (Stripe) Volume or How to Create a RAID 0 (Concatenation) Volume.
-
To create the mirror, use one of the following methods:
-
From the Enhanced Storage tool within the Solaris Management Console, open the Volumes node, then choose Action->Create
Volume and follow the instructions on screen. For more information, see the
online help.
-
Use the following form of the metainit
command to create a one-way mirror:
metainit {volume-name} [-m ] {submirror-name…}
-
volume-name is the name of the
volume to create.
-
-m specifies to create a mirror.
-
submirror-name specifies the name
of the component that will be the first submirror in the mirror.
See the following examples and the metainit(1M) man page for more information.
-
To add the second submirror, use one of the following methods:
-
From the Enhanced Storage tool within the Solaris Management Console, open the Volumes node, then choose the
mirror you want to modify. Choose Action->Properties, then the Submirrors
tab and follow the instructions on screen to Attach Submirror. For more information,
see the online help.
-
Use the following form of the metattach
command:
metattach {mirror-name} {new-submirror-name…}
See the following examples and the metattach(1M) man page for more information.
Example—Creating a Two-Way Mirror
# metainit d51 1 1 c0t0d0s2
d51: Concat/Stripe is setup
# metainit d52 1 1 c1t0d0s2
d52: Concat/Stripe is setup
# metainit d50 -m d51
d50: Mirror is setup
# metattach d50 d52
d50: Submirror d52 is attached
|
This example shows the creation of a two-way mirror, d50.
The metainit command creates two submirrors (d51 and d52), which are RAID 0 volumes. The metainit -m command creates the one-way mirror from
the d51 RAID 0 volume. The metattach
command attaches d52, creating a two-way mirror and causing
a resynchronization. (Any data on the attached submirror is overwritten by
the other submirror during the resynchronization.) The system verifies that
the objects are defined.
Example—Creating a Two-Way Mirror Without Resynchronization
# metainit d51 1 1 c0t0d0s2
d51: Concat/Stripe is setup
# metainit d52 1 1 c1t0d0s2
d52: Concat/Stripe is setup
# metainit d50 -m d51 d52
metainit: d50: WARNING: This form of metainit is not recommended.
The submirrors may not have the same data.
Please see ERRORS in metainit(1M) for additional information.
d50: Mirror is setup
|
This example creates a two-way mirror, d50. The metainit command creates two submirrors (d51
and d52), which are RAID 0 volumes. The metainit -m command with both submirrors creates the mirror
from the d51 RAID 0 volume and avoids resynchronization.
It is assumed that all information on the mirror is considered invalid and
will be regenerated (for example, through a newfs operation)
before the mirror is used.
Where to Go From Here
To prepare a newly created mirror for a file system, see “Creating File Systems (Tasks)” in System Administration Guide: Basic Administration.
An application, such as a database, that uses the raw volume must have its
own way of recognizing the volume.
How to Create a RAID 1 Volume From a File System
Use this procedure to mirror an
existing file system. If the file system can be unmounted, the entire procedure
can be completed without a reboot. For file systems (such as root (/)) that cannot be unmounted, the system will have to be rebooted
to complete the procedure.
Note –
When mirroring root (/), it is essential
that you record the secondary root slice name to reboot the system if the
primary submirror fails. This information should be written down, not recorded
on the system, which might not be available. See Chapter 24, Troubleshooting Solaris Volume Manager
for details on recording the alternate boot device, and on booting from the
alternate boot device.
If you are mirroring root on an IA system, install the boot information
on the alternate boot disk before you create the RAID 0 or RAID 1 devices.
See “SPARC: Booting a System (Tasks)” in System Administration
Guide: Basic Administration.
In this procedure, an existing device is c1t0d0s0.
A second device, c1t1d0s0, is available for the second
half of the mirror. The submirrors will be d1 and d2, respectively, and the mirror will be d0.
-
Check Prerequisites for Creating Solaris Volume Manager Elements and Background Information for Creating RAID 1 Volumes.
-
Identify the slice that contains the existing file system to be mirrored
(c1t0d0s0 in this example).
-
Create a new RAID 0 volume on the slice from the previous step by using
one of the following methods:
-
From the Enhanced Storage tool within the Solaris Management Console, open the Volumes node, then choose Action->Create
Volume and follow the instructions on screen. For more information, see the
online help.
-
Use the metainit raid-0-volume-name -f 1 1 ctds-of-slice command.
# metainit d1 -f 1 1 c1t0d0s0
|
-
Create a second RAID 0 volume (concatenation) on an unused slice (c1t1d0s0 in this example) to act as the second submirror. The second
submirror must be the same size as the original submirror or larger. Use one
of the following methods:
-
From the Enhanced Storage tool within the Solaris Management Console, open the Volumes node, then choose Action->Create
Volume and follow the instructions on screen. For more information, see the
online help.
-
Use the metainit second-raid-0-volume-name 1 1 ctds-of-slice command.
# metainit d2 1 1 c1t1d0s0
|
-
Create a one-way mirror by using one of the following methods:
-
From the Enhanced Storage tool within the Solaris Management Console, open the Volumes node, then choose Action->Create
Volume and follow the instructions on screen. For more information, see the
online help.
-
Use the metainit mirror-name -m raid-0-volume-name command.
See the metainit(1M)
man page for more information.
Note –
When you create a mirror from an existing file system, you must
follow the next two steps precisely to avoid data corruption.
If you are mirroring any file system other than the root (/) file system, then edit the /etc/vfstab file
so that the file system mount instructions refer to the mirror, not to the
block device.
For more information about the/etc/vfstab file,
see“Mounting File Systems ()” in System Administration Guide:
Basic Administration.
-
Remount your newly mirrored file system according to one of the following
procedures:
-
If you are mirroring your root (/) file
system, run the metaroot d0
command, replacing d0 with the name of the mirror you just
created, then reboot your system.
For more information, see the metaroot(1M) man page.
-
If you are mirroring a file system that can be unmounted,
then unmount and remount the file system.
-
If you are mirroring a file system other than root (/) that cannot be unmounted, then reboot your system.
-
Use the metattach command to attach the second submirror.
See the metattach(1M) man page for more information.
-
If you mirrored your root file system, record the alternate boot path.
See How to Record the Path to the Alternate Boot Device.
Caution –
Be sure to create a one-way mirror with the metainit command then attach the additional submirrors with the metattach command. When the metattach command
is not used, no resynchronization operations occur. As a result, data could
become corrupted when Solaris Volume Manager assumes that both sides of the mirror
are identical and can be used interchangably.
Example—Creating a Two-Way Mirror (Unmountable File System)
# metainit -f d1 1 1 c1t0d0s0
d1: Concat/Stripe is setup
# metainit d2 1 1 c1t1d0s0
d2: Concat/Stripe is setup
# metainit d0 -m d1
d0: Mirror is setup
# umount /master
(Edit the /etc/vfstab file so that the file system references the mirror)
# mount /master
# metattach d0 d2
d0: Submirror d2 is attached
|
The -f option forces the creation of the first concatenation, d1, which contains the mounted file system /master
on /dev/dsk/c1t0d0s0. The second concatenation, d2, is created from /dev/dsk/c1t1d0s0. (This
slice must be the same size or greater than that of d1.)
The metainit command with the -m option
creates the one-way mirror, d0, from d1.
Next, the entry for the file system should be changed in the /etc/vfstab file to reference the mirror. For example, the following
line:
/dev/dsk/c1t0d0s0 /dev/rdsk/c1t0d0s0 /var ufs 2 yes -
|
should be changed to:
/dev/md/dsk/d0 /dev/md/rdsk/d0 /var ufs 2 yes -
|
Finally, the file system is remounted and submirror d2
is attached to the mirror, causing a mirror resynchronization. The system
confirms that the RAID 0 and RAID 1 volumes are set up, and that submirror d2 is attached.
Example—Creating a Mirror From root (/)
# metainit -f d1 1 1 c0t0d0s0
d11: Concat/Stripe is setup
# metainit d2 1 1 c0t1d0s0
d12: Concat/Stripe is setup
# metainit d0 -m d1
d10: Mirror is setup
# metaroot d0
# lockfs -fa
# reboot
...
# metattach d0 d2
d10: Submirror d12 is attached
# ls -l /dev/rdsk/c0t1d0s0
lrwxrwxrwx 1 root root 88 Feb 8 15:51 /dev/rdsk/c1t3d0s0 ->
../../devices/iommu@f,e0000000/vme@f,df010000/SUNW,pn@4d,1080000/ipi3sc@0,0/i
d@3,0:a,raw
|
Note –
Do not attach the second submirror before the system is rebooted.
You must reboot between running the metaroot command and
attaching the second submirror.
The -f option forces the creation of the first RAID
0 volume, d1, which contains the mounted file system
root (/) on /dev/dsk/c0t0d0s0. The
second concatenation, d2, is created from /dev/dsk/c0t1d0s0. (This slice must be the same size or greater
than that of d1.) The metainit command
with the -m option creates the one-way mirror d0 using the concatenation that contains root (/).
Next, the metaroot command edits the /etc/vfstab and /etc/system files so that the system
can be booted with the root file system (/) on a volume. (It is a good idea
to run the lockfs -fa command before rebooting.)
After a reboot, the submirror d2 is attached to the mirror,
causing a mirror resynchronization. (The system confirms that the concatenations
and the mirror are set up, and that submirror d2 is attached.)
The ls -l command is run on the root raw
device to determine the path to the alternate root device in case the system
might later need to be booted from it.
Example—Creating a Two-way Mirror (File System That Cannot Be
Unmounted—/usr)
# metainit -f d12 1 1 c0t3d0s6
d12: Concat/Stripe is setup
# metainit d22 1 1 c1t0d0s6
d22: Concat/Stripe is setup
# metainit d2 -m d12
d2: Mirror is setup
(Edit the /etc/vfstab file so that /usr references the mirror)
# reboot
...
# metattach d2 d22
d2: Submirror d22 is attached
|
The -f option forces the creation of the first concatenation, d12, which contains the mounted file system /usr
on /dev/dsk/c0t3d0s6. The second concatenation, d22, is created from /dev/dsk/c1t0d0s6. (This
slice must be the same size or greater than that of d12.)
The metainit command with the -m option
creates the one-way mirror d2 using the concatenation
containing /usr. Next, the /etc/vfstab
file must be edited to change the entry for /usr to reference
the mirror. For example, the following line:
/dev/dsk/c0t3d0s6 /dev/rdsk/c0t3d0s6 /usr ufs 1 yes -
|
should be changed to:
/dev/md/dsk/d2 /dev/md/rdsk/d2 /usr ufs 1 yes -
|
After a reboot, the second submirror d22 is attached
to the mirror, causing a mirror resynchronization. (The system confirms that
the concatenation and the mirror are set up, and that submirror d22 is attached.
Example—Creating a Mirror From swap
# metainit -f d11 1 1 c0t0d0s1
d11: Concat/Stripe is setup
# metainit d21 1 1 c1t0d0s1
d21: Concat/Stripe is setup
# metainit d1 -m d11
d1: Mirror is setup
(Edit the /etc/vfstab file so that swap references the mirror)
# reboot
...
# metattach d1 d21
d1: Submirror d21 is attached
|
The -f option forces the creation of the first concatenation, d11, which contains the mounted file system swap
on /dev/dsk/c0t0d0s1. The second concatenation, d21, is created from /dev/dsk/c1t0d0s1. (This
slice must be the same size or greater than that of d11.)
The metainit command with the -m option
creates the one-way mirror d1 using the concatenation
that contains swap. Next, if there is an entry for swap in the /etc/vfstab file, it must be edited
to reference the mirror. For example, the following line:
/dev/dsk/c0t0d0s1 - - swap - no -
|
should be changed to:
/dev/md/dsk/d1 - - swap - no -
|
After a reboot, the second submirror d21 is attached
to the mirror, causing a mirror resynchronization. (The system confirms that
the concatenations and the mirror are set up, and that submirror d21 is attached.
To save the crash dump when you have mirrored swap,
use the dumpadm command to configure the dump device as
a volume. For instance, if the swap device is named /dev/md/dsk/d2, use the dumpadm command to set this device
as the dump device.
Mirroring root (/) Special Considerations
The process for mirroring root (/) is the same
as in mirroring any other file system that you cannot unmount, with the exception
that you run the metaroot command instead of manually editing
the /etc/vfstab file. See How to Create a RAID 1 Volume From a File System.
The following sections outline special considerations and issues for mirroring
root (/) file systems.
How to Record the Path to the Alternate Boot Device
When you are mirroring root (/), you might need
the path to the alternate boot device later if the primary device fails. The
process for finding and recording the alternate boot device differs, depending
on your system's architecture. See SPARC: Example—Recording the Alternate Boot Device Path or x86: Example—Recording the Alternate Boot Device Path.
SPARC: Example—Recording the Alternate Boot Device Path
In this example, you determine the path to the alternate root device
by using the ls -l command on the slice
that is being attached as the second submirror to the root (/)
mirror.
# ls -l /dev/rdsk/c1t3d0s0
lrwxrwxrwx 1 root root 55 Mar 5 12:54 /dev/rdsk/c1t3d0s0 -> \
../../devices/sbus@1,f8000000/esp@1,200000/sd@3,0:a
|
Here you would record the string that follows the /devices directory: /sbus@1,f8000000/esp@1,200000/sd@3,0:a.
Solaris Volume Manager users who are using a system with OpenBootTM Prom can use the OpenBoot nvalias command
to define a “backup root” device alias for the secondary root
(/) mirror. For example:
ok nvalias backup_root /sbus@1,f8000000/esp@1,200000/sd@3,0:a
|
Then, redefine the boot-device alias to reference
both the primary and secondary submirrors, in the order in which you want
them to be used, and store the configuration.
ok printenv boot-device
boot-device = disk net
ok setenv boot-device disk backup-root net
boot-device = disk backup-root net
ok nvstore
|
In the event of primary root disk failure, the system would automatically
boot to the second submirror. Or, if you boot manually, rather than using
auto boot, you would only enter:
x86: Example—Recording the Alternate Boot Device Path
In this example, you would determine the path to the alternate boot
device by using the ls -l command on the
slice that is being attached as the second submirror to the root (/) mirror.
# ls -l /dev/rdsk/c1t0d0s0
lrwxrwxrwx 1 root root 55 Mar 5 12:54 /dev/rdsk/c1t0d0s0 -> ../.
./devices/eisa/eha@1000,0/cmdk@1,0:a
|
Here, you would record the string that follows the /devices directory: /eisa/eha@1000,0/cmdk@1,0:a
Booting From Alternate Boot Devices
If your primary submirror on a mirrored root (/)
fails, you will need to initiate the boot from the other submirror. You can
either configure the system to boot automatically from the second side of
the mirror, or can manually boot from the second side.
See “SPARC: Booting a System (Tasks)” in System Administration
Guide: Basic Administration
Working with Submirrors
How to Attach a Submirror
-
Identify the component (concatenation or stripe) to be used as a submirror.
It must be the same size (or larger) as the existing submirror in the
mirror. If you have not yet created a volume to be a submirror, see Creating RAID 0 (Stripe) Volumes or Creating RAID 0 (Concatenation) Volumes.
-
Make sure that you have root privilege and that you have a current backup
of all data.
-
Use one of the following methods to attach a submirror.
-
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 mirror submirror command.
# metattach mirror submirror
|
See the metattach(1M)
man page for more information.
Example—Attaching a Submirror
# metastat d30
d30: mirror
Submirror 0: d60
State: Okay
...
# metattach d30 d70
d30: submirror d70 is attached
# metastat d30
d30: mirror
Submirror 0: d60
State: Okay
Submirror 1: d70
State: Resyncing
Resync in progress: 41 % done
Pass: 1
Read option: roundrobin (default)
Write option: parallel (default)
Size: 2006130 blocks
...
|
This example shows the attaching of a submirror, d70,
to a one-way mirror, d30, creating a two-way mirror.
The mirror d30 initially consists of submirror d60. The submirror d70 is a RAID 0 volume.
You verify that the status of the mirror is “Okay” with the metastat command, then attach the submirror. When the metattach command is run, the new submirror is resynchronized with
the existing mirror. When you attach an additional submirror to the mirror,
the system displays a message. To verify that the mirror is resynchronizing,
use the metastat command.
How to Detach a Submirror
-
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 detach a submirror.
-
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 metadetach command to detach a
submirror from a mirror.
# metadetach mirror submirror
|
See the metadetach(1M) man page for more information.
Example—Detaching a Submirror
# metastat
d5: mirror
Submirror 0: d50
...
# metadetach d5 d50
d5: submirror d50 is detached
|
In this example, mirror d5 has a submirror, d50, which is detached with the metadetach command.
The underlying slices from d50 are going to be reused
elsewhere. When you detach a submirror from a mirror, the system displays
a confirmation message.
How to Place a Submirror Offline and Online
The metaonline
command can only be used when a submirror was taken offline by the metaoffline command. After the metaonline command
runs, Solaris Volume Manager automatically begins resynchronizing the submirror with
the mirror.
Note –
The metaoffline command's capabilities are
similar to that offered by the metadetach command. However,
the metaoffline command does not sever the logical association
between the submirror and the mirror.
-
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 place a submirror online or offline.
-
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 metaoffline command to take offline
a submirror.
# metaoffline mirror submirror
|
See the metaoffline(1M)
man page for more information.
-
Use the metaonline command to bring a submirror
online.
# metaonline mirror submirror
|
See the metaonline(1M)
man page for more information.
Example—Placing a Submirror Offline
# metaoffline d10 d11
d10: submirror d11 is offlined
|
In this example, submirror d11 is taken offline
from mirror d10. Reads will continue to be made from
the other submirror. The mirror will be out of sync as soon as the first write
is made. This inconsistency is corrected when the offlined submirror is brought
back online.
Example—Placing a Submirror Online
# metaonline d10 d11
d10: submirror d11 is onlined
|
In this example, submirror d11 is brought back
online in mirror d10.
How to Enable a Slice in a Submirror
-
Make sure that you have root privilege and that you have a current backup
of all data.
-
Read Overview of Replacing and Enabling Components in RAID 1 and RAID 5
Volumes and Background Information for RAID 1 Volumes.
-
Use one of the following methods to enable a slice in a submirror.
-
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 metareplace command to enable a
failed slice in a submirror.
# metareplace -e mirror failed-slice
|
The metareplace command automatically starts a resynchronization
to synchronize the repaired or replaced slice with the rest of the mirror.
See the metareplace(1M)
man page for more information.
Example—Enabling a Slice in a Submirror
# metareplace -e d11 c1t4d0s7
d11: device c1t4d0s7 is enabled
|
In this example, the mirror d11 has a submirror
that contains slice, c1t4d0s7, which had a soft error.
The metareplace command with the -e option
enables the failed slice.
Note –
If a physical disk is defective, you can either replace it with
another available disk (and its slices) on the system as documented in How to Replace a Slice in a Submirror. Alternatively, you can repair/replace the
disk, format it, and run the metareplace command with the -e option as shown in this example.
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 Grow a File System.
An application, such as a database, that uses the raw volume must have
its own way of growing the added space.
Responding to RAID 1 Volume Component Failures
How to Replace a Slice in a Submirror
-
Make sure that you have root privilege and that you have a current backup
of all data.
-
Read Overview of Replacing and Enabling Components in RAID 1 and RAID 5
Volumes and Background Information for RAID 1 Volumes.
-
Use one of the following methods to replace a slice in 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 following form of the metareplace
command to replace a slice in a submirror:
metareplace {mirror-name} {component-name…}
See the following examples and the metainit(1M) man page for more information.
Example—Replacing a Failed Slice in a Mirror
The following example illustrates how to replace a failed slice when
the system is not configured to use hot spare pools for the automatic replacement
of failed disks. See Chapter 15, Hot Spare Pools (Overview) for more information
about using hot spare pools.
# metastat d6
d6: Mirror
Submirror 0: d16
State: Okay
Submirror 1: d26
State: Needs maintenance
...
d26: Submirror of d6
State: Needs maintenance
Invoke: metareplace d6 c0t2d0s2 <new device>
...
# metareplace d6 c0t2d0s2 c0t2d2s2
d6: device c0t2d0s2 is replaced with c0t2d2s2
|
The metastat command confirms that mirror d6 has a submirror, d26, with a slice in the “Needs
maintenance” state. The metareplace command replaces
the slice as specified in the “Invoke” line of the metastat output with another available slice on the system. The system confirms
that the slice is replaced, and starts resynchronizing the submirror.
How to Replace a Submirror
-
Make sure that you have root privilege and that you have a current backup
of all data.
-
Read Overview of Replacing and Enabling Components in RAID 1 and RAID 5
Volumes and Background Information for RAID 1 Volumes.
-
Use one of the following methods to replace a submirror.
-
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 metadetach, metaclear, metatinit, and metattach
commands to replace an entire submirror.
Example—Replacing a Submirror in a Mirror
The following example illustrates how to replace a submirror in an active
mirror.
Note –
The specific configuration of the new volume d22
will depend on the component you are replacing. A concatenation, as shown
here, would be fine to replace a concatenation, but would not be an ideal
replacement for a stripe as it could impact performance.
# metastat d20
d20: Mirror
Submirror 0: d21
State: Okay
Submirror 1: d22
State: Needs maintenance
...
# metadetach -f d20 d22
d20: submirror d22 is detached
# metaclear -f d22
d22: Concat/Stripe is cleared
# metainit d22 2 1 c1t0d0s2 1 c1t0d1s2
d22: Concat/Stripe is setup
# metattach d20 d22
d20: components are attached
|
The metastat command confirms that the two-way mirror d20 has a submirror, d22, in the “Needs
maintenance” state. In this case, the entire submirror will be cleared
and recreated. The metadetach command detaches the failed
submirror from the mirror by using the -f option, which forces
the detach to occur. The metaclear command clears the submirror.
The metainit command recreates submirror d22, with new slices. The metattach command attaches
the rebuilt submirror, and a mirror resynchronization begins automatically.
Note –
You temporarily lose the capability for data redundancy while
the mirror is a one-way mirror.
Removing RAID 1 Volumes (Unmirroring)
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.
-
Make sure that you have root privilege and that you have a current backup
of all data.
-
Read Background Information for RAID 1 Volumes.
-
Verify that at least one submirror is in the Okay state.
-
Unmount the file system.
-
Detach the submirror that will continue to be used for the file system
For more information, see the metadetach(1M) man page.
-
Clear the mirror and remaining subcomponents.
For more information, see the metaclear(1M)
-
Edit the /etc/vfstab file to use the component
detached in Step 5, if necessary.
-
Remount the file system.
Example—Unmirroring the /opt File System
# metastat d4
d4: Mirror
Submirror 0: d2
State: Okay
Submirror 1: d3
State: Okay
...
# 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 filesystem is made of
a two-way mirror named d4; its submirrors are d2 and d3, made of slices /dev/dsk/c0t0d0s0 and /dev/dsk/c1t0d0s0, respectively. 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. For example,
if d4 were the mirror and d2 the
submirror, the following line:
/dev/md/dsk/d4 /dev/md/rdsk/d4 /var ufs 2 yes -
|
should be changed to:
/dev/md/dsk/d2 /dev/md/rdsk/d2 /var 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.
Note –
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 that cannot be unmounted during
normal system operation, including root (/), /usr, /opt, and swap.
-
Run the metastat command to verify that at least
one submirror is in the “Okay” state.
-
Run the metadetach command on the mirror that contains
root (/), /usr, /opt,
or swap to make a one-way mirror.
-
For /usr, /opt, and swap: change the file system entry in the /etc/vfstab file to use a non-Solaris Volume Manager device (slice).
-
For root (/) only: running the metaroot command.
-
Reboot the system.
-
Run the metaclear command to clear the mirror and
submirrors.
Example—Unmirroring root (/)
# 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, root (/) is a two-way mirror named d0; its submirrors are d10 and d20, which are made of slices /dev/dsk/c0t3d0s0
and /dev/dsk/c1t3d0s0, respectively. The metastat command verifies that at least one submirror is in the “Okay”
state. (A mirror with no submirrors in the “Okay” state must first
be repaired.) Submirror d20 is detached to make d0 a one-way mirror. The metaroot command is
then run, using the rootslice from which the system
is going to boot. This command edits the /etc/system
and /etc/vfstab files to remove information that specifies
the mirroring of root (/). After a reboot, the metaclear -r command deletes the mirror and the
other submirror, d10. The last metaclear
command clears submirror d20.
Example—Unmirroring swap
# 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, swap is made of a two-way mirror
named d1; its submirrors are d11
and d21, which are made of slices /dev/dsk/c0t3d0s1 and /dev/dsk/c1t3d0s1, respectively. The metastat command verifies that at least one submirror is in the “Okay”
state. (A mirror with no submirrors in the “Okay” state must first
be repaired.) Submirror d21 is detached to make d1 a one-way mirror. Next, the /etc/vfstab
file must be edited to change the entry for swap to reference
the slice that is in submirror d21. For example, if d1 was the mirror, and d21 the submirror containing
slice /dev/dsk/c0t3d0s1, the following line:
/dev/md/dsk/d1 - - swap - no -
|
should be changed to:
/dev/dsk/c0t3d0s1 - - swap - no -
|
After a reboot, the metaclear -r
command deletes the mirror and the other submirror, d11.
The final metaclear command clears submirror d21.
Using a Mirror to Back Up Data
Although Solaris Volume Manager is not meant to be a “backup product,”
it does provide a means for backing up mirrored data without unmounting the
mirror or taking the entire mirror offline, and without halting the system
or denying users access to data. This process happens as follows: one of the
submirrors is taken offline, temporarily losing the mirroring, and backed
up. That submirror is then placed online and resynchronized as soon as the
backup is complete.
How to Use a RAID 1 Volume to Make an Online Backup
You can use this procedure on any file system except root (/). Be aware that this type of backup creates a “snapshot”
of an active file system. Depending on how the file system is being used when
it is write-locked, some files and file content on the backup might not correspond
to the actual files on disk.
The following limitations apply to this procedure:
-
If you use this procedure on a two-way mirror, be aware that
data redundancy is lost while one submirror is offline for backup. A three-way
mirror does not have this problem.
-
There is some overhead on the system when the offlined submirror
is brought back online after the backup is complete.
The high-level steps in this procedure are as follows:
-
Write-locking the file system (UFS only). Do not lock root
(/).
-
Using the metaoffline command to take one
submirror offline from the mirror
-
Unlocking the file system
-
Backing up the data on the offlined submirror
-
Using the metaonline command to place the
offlined submirror back online
Note –
If you use these procedures regularly, put them into a script
for ease of use.
-
Run the metastat command to make sure the mirror
is in the “Okay” state.
A mirror that is in the “Maintenance” state should be repaired
first.
-
For all file systems except root (/), lock the
file system from writes.
# /usr/sbin/lockfs -w mount point
|
Only a UFS needs to be write-locked. If the volume is set up as a raw
device for database management software or some other application, running lockfs is not necessary. (You might, however, want to run the appropriate
vendor-supplied utility to flush any buffers and lock access.)
Caution – Write-locking root (/) causes the system
to hang, so it should never be performed.
-
Take one submirror offline from the mirror.
# metaoffline mirror submirror
|
In this command:
-
mirror
-
Is the volume name of the mirror.
-
submirror
-
Is the volume name of the submirror (volume) being taken offline.
Reads will continue to be made from the other submirror.
The mirror will be out of sync as soon as the first write is made. This inconsistency
is corrected when the offlined submirror is brought back online in Step 6.
There is no need to run the fsck command on the offlined
file system.
-
Unlock the file system and allow writes to continue.
# /usr/sbin/lockfs -u mount-point
|
You might need to perform necessary unlocking procedures based on vendor-dependent
utilities used in Step 2 above.
-
Perform a backup of the offlined submirror.
Use the ufsdump command or your usual backup utility.
Note –
To ensure a proper backup, use the raw volume,
for example, /dev/md/rdsk/d4. Using “rdsk” allows greater than 2 Gbyte access.
-
Place the submirror back online.
# metaonline mirror submirror
|
Solaris Volume Manager automatically begins resynchronizing the submirror with
the mirror.
Example—Using a Mirror to Make an Online Backup
This example uses a mirror named d1, consisting
of submirrors d2 and d3. The submirror d3 is taken offline and backed up while submirror d2 stays online. The file system on the mirror is /home1.
# /usr/sbin/lockfs -w /home1
# metaoffline d1 d3
d1: submirror d3 is offlined
# /usr/sbin/lockfs -u /home1
(Perform backup using /dev/md/rdsk/d3)
# metaonline d1 d3
d1: submirror d3 is onlined
|
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