Once
a shadow set is created, you can add and remove individual members
by mounting or dismounting physical disk devices. The shadowing software
allows you to add and remove shadow set members at any time, transparently
to user processes or applications running on the system.
Adding a Disk to an Existing Shadow Set |
 |
The following command shows how to add the disk
$4$DUA3 to the DSA23 shadow set:
$ MOUNT/CONFIRM/SYSTEM DSA23: /SHADOW=($4$DUA9,$4$DUA3)volume-label |
The command specifies both the currently active
shadow set member ($4$DUA9) and the new member ($4$DUA3). Although
it is not necessary to include them when mounting additional physical
devices, you can specify current shadow set members without affecting
their membership state.
Note that when you add volumes to an existing
shadow set mounted across an OpenVMS Cluster system, the shadowing
software automatically adds the new members on each OpenVMS Cluster
node.
Creating a Two-Member Shadow Set and Adding a Third Member |
|
Example 4-4 shows how to create
a two-member shadow set with the first command and how to add another
member to the shadow set with the second command.
Example 4-4 Creating a Shadow Set and Adding Third Member
$MOUNT/SYSTEM DSA4: /SHADOW = ($3$DIA7:, $3$DIA8:) FORMERSELF |
%MOUNT-I-MOUNTED, FORMERSELF mounted on DSA4:
%MOUNT-I-SHDWMEMSUCC, _$3$DIA7: (DISK300) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMSUCC, _$3$DIA8: (DISK301) is now a valid member of
the shadow set
$MOUNT/SYSTEM DSA4: /SHADOW = $3$DIA6: FORMERSELF |
%MOUNT-I-SHDWMEMCOPY, _$3$DIA6: (DISK302) added to the shadow set
with a copy operation |
In this example, the first command creates a shadow
set whose virtual unit name is DSA4. The member disks are $3$DIA7
and $3$DIA8. The second command mounts the disk $3$DIA6 and adds it
to shadow set DSA4. The shadow set now includes three members: $3$DIA6,
$3$DIA7, and $3$DIA8. In this example, when you add $3$DIA6 after
the shadow set already exists, the added volume becomes the target
of a copy operation.
Checking Status of Potential Shadow Set Members With /CONFIRM |
|
When you add a disk to an existing shadow set, a copy operation is
necessary. Volume shadowing automatically performs the copy operation,
unless you use the /CONFIRM qualifier or the /NOCOPY qualifier. When
you specify the /CONFIRM qualifier, as shown in Example 4-5, the MOUNT command
displays the targets of copy operations and prompts for permission
before the operations are performed. This precaution can prevent the
erasure of important data. For more information about copy operations,
see Chapter 6.
Example 4-5 Using the /CONFIRM Qualifier
$MOUNT/CONFIRM DSA23: /SHADOW=($1$DUA4:,$1$DUA6:) SHADOWVOL
%MOUNT-F-SHDWCOPYREQ, shadow copy required
Virtual Unit - DSA23 Volume Label - SHADOWVOL |
Member Volume Label Owner UIC |
$1$DUA6: (LOVE) SCRATCH [100,100]
Allow FULL shadow copy on the above member(s)? [N]:NO
$ |
This command instructs MOUNT to build a shadow
set with the specified devices and to prompt for permission to perform
any copy operations.
Because a copy operation is necessary, the virtual
unit name and the volume label are displayed.
The display also includes the physical device
name, the volume label, and the volume owner of the potential shadow
set member that requires the copy operation.
A response of No causes MOUNT to quit without
mounting or copying.
Checking Status of Potential Shadow Set Members With /NOCOPY |
|
When you specify more than one disk, the shadowing
software automatically determines the correct copy operation to perform
in order to make shadow set members consistent with each other (see “Copy Operations” for details).
The Mount utility interprets information recorded on each member to
determine whether a member requires a copy operation, a merge operation,
or no copy operation. If you are not sure which disks might be targets
of copy operations, you can specify the /CONFIRM qualifier or the
/NOCOPY qualifier as a precaution against overwriting important data
when you mount a disk. With the /NOCOPY qualifier, you disable the
copy operation.
Example 4-6 shows how to use the /NOCOPY qualifier to check the status of potential
shadow set members before any data is erased.
Example 4-6 Using the /NPCOPY Qualifier
$MOUNT/NOCOPY DSA2: /SHADOW=($1$DUA4:,$1$DUA6:,$1$DUA7:) -
_$SHADOWVOL DISK$SHADOWVOL |
%MOUNT-F-SHDWCOPYREQ, shadow copy required
%MOUNT-I-SHDWMEMFAIL, DUA7: failed as a member of the shadow set
%MOUNT-F-SHDWCOPYREQ, shadow copy required |
$ MOUNT/COPY DSA2: /SHADOW=($1$DUA4:,$1$DUA6:,$1$DUA7:) -
_$SHADOWVOL DISK$SHADOWVOL
%MOUNT-I-MOUNTED, SHADOWVOL mounted on _DSA2:
%MOUNT-I-SHDWMEMSUCC, _$1$DUA4: (VOLUME001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMSUCC, _$1$DUA6: (VOLUME002) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA7: (VOLUME003) added to the shadow set
with a copy operation |
The first command in this example instructs MOUNT
to build a shadow set, with the specified devices, but only if a copy
or merge operation is not required.
In this example, MOUNT did not build the shadow
set because the specified disk, loaded on device $1$DUA7, required
a copy operation. At this point, you can verify that the volume in
device $1$DUA7 does not contain any useful data.
If the device does not contain valuable data,
you can reenter the MOUNT command, as shown in this example, and include
the /COPY qualifier. This command instructs MOUNT to mount a shadow
set and to proceed with the necessary copy or merge operation.
The resulting MOUNT status messages show that
the shadow set is successfully mounted. The $1$DUA7 device is currently
the target of a copy operation; it attains full shadow set membership
when the copy operation completes.