Use the Add Copy to
VDisk panel in the SAN Volume Controller Console to
add a copy to the selected virtual disk (VDisk). Each VDisk can
have a maximum of two copies.
Introduction
You
can create mirrored copies of a VDisk so that the VDisk remains accessible
even if a managed disk (MDisk) that it depends on becomes unavailable.
You can create copies of a VDisk from different MDisk groups or create an
image mode copy of the VDisk. VDisk copies
keep data available, but they are not separate objects; they can be created
or changed only from the VDisk.
In addition, you can add
a copy to a VDisk as an alternative
method of migrating VDisks between MDisk groups. For example, if you
have a nonmirrored VDisk in one MDisk group and want to migrate that
VDisk to a second MDisk group, you can add a new copy of the VDisk
by specifying the second MDisk group for that VDisk copy. After the
copies have synchronized, you can delete the copy in the first MDisk
group.
This alternative method has the following
advantages:
- Access to the VDisk data is not lost if the second
MDisk group
goes offline during the migration.
- The speed of the migration
can be adjusted using the VDisk synchronization
rate, and the migration can be paused.
- The migration can be
ended by deleting the VDisk copy in the second
MDisk group before migration completes.
- MDisk
groups can have different extent sizes.
This
alternative method has the following
limitations:
- You cannot use this method for VDisks that are
already mirrored.
- There are more manual steps that are associated
with this method.
- Write I/O performance is slightly impacted
during the migration,
because the mirrored copies must be kept synchronized.
Options
are dynamic based on the type of VDisk copy that
you choose to add.
Attributes
The
following attributes are displayed:
- VDisk Capacity
- Displays the current capacity for the VDisk.
- Copy 0 MDisk Group
- Displays the name of the managed disk
(MDisk) group that is associated
with the VDisk that you are creating a copy of.
Fields
The
following fields can be updated:
- Select the type
of virtual disk
- Select the type of VDisk copy. Additional
options on this panel
are dynamic based on these selections. The following values are possible:
- Striped
- Select this option to create
the copy of the VDisk
from multiple MDisks that are in the MDisk group. Extents are allocated
on the MDisks in the specified order. The following fields are available
when you select to add a striped VDisk copy:
- Managed
Disk Group
- Select the available MDisk group from which you
can create a VDisk
copy.
- Select MDisks manually
- Select
this option to manually select MDisks that
will be used to create the VDisk copy.
- Managed
Disk Candidates
- Select the MDisk that will be
used to allocate new
extents to the VDisk copy. Click Add to add
the selected MDisk to the Selected MDisk list.
After you have added all the MDisks to use to add the VDisk copy,
you can use the arrows to determine the order that they are used.
- Synchronization Rate
- Specify
the synchronization rate. A value of zero
(0) prevents synchronization. The default value is 50 (2 MB per second).
The following table shows the relationship of the
rate value to the data copied per second.
Table 1. Relationship between the rate value
and the data copied per second| User-specified rate attribute value |
Data copied/sec |
|---|
| 1 - 10 |
128 KB |
| 11 - 20 |
256 KB |
| 21 - 30 |
512 KB |
| 31 - 40 |
1 MB |
| 41 - 50 |
2 MB |
| 51 - 60 |
4 MB |
| 61 - 70 |
8 MB |
| 71 - 80 |
16 MB |
| 81 - 90 |
32 MB |
| 91 - 100 |
64 MB |
- Create copies in synch
- Select
this option to create synchronized copies. Select this
option when MDisks are already formatted or when read stability to
unwritten areas of the VDisk is not required.
- Space-efficient
- Select this option to create a space-efficient
copy of the VDisk.
If you select this option, these additional options are available:
- Real size to initially allocate
- Specify
the disk space to be allocated for the space-efficient
copy of the selected VDisk. Setting the real space for a space-efficient
copy protects the copy from going offline when its MDisk group runs
out of space. You can either specify a percentage of the VDisk's capacity
for the copy or enter a specific amount of real capacity to allocate.
If you enter a specific amount, you must also select the units for
the space. You can select the following units: B, KB, MB, GB, TB,
and PB.
- Warn when used capacity of VDisk
reaches
- Specify a threshold to send a warning
message for
the VDisk copy when the capacity that is used first exceeds the specified
level. You can either specify a percentage of VDisk capacity or enter
a specific amount of capacity to be allocated. If you enter a specific
amount, you must also select the units for the space. You can select
the following units: B, KB, MB, GB, TB, and PB. If you select Autoexpand,
the default value for the warning level is 80% of the virtual disk
capacity. If Autoexpand is not selected, the
default value for the warning level is 80% of the real capacity. To
disable warnings, specify 0 or 0%.
- Autoexpand
- Select this option if you want the space-efficient copies to automatically
expand their real capacities by allocating new extents from their
MDisk group.
- Grain size
- Select
the grain size in kilobytes (KB) for a space-efficient
copy of the VDisk. The following values are possible:
- Format the
new VDisk copy and mark the VDisk synchronized
- Select this
option to format the VDisk copy and synchronize the
copy with the primary copy of the VDisk.
- Sequential
- Select
this option to create the copy of the VDisk
from one MDisk that is in the MDisk group. Extents are sequentially
allocated on the MDisk. The following fields are available when you
select to add a sequential VDisk copy:
- Managed Disk
Group
- Select the available MDisk group from which you can
create a VDisk
copy.
- Select MDisk(s) manually
- Select
this option to manually select MDisks to use to create
the VDisk copy. For a sequential VDisk copy, this option is disabled.
- Choose 1 managed disks
- Select the MDisk
to use to allocate new extents to the VDisk copy.
- Synchronization Rate
- Specifies the
copy synchronization rate. A value
of zero (0) prevents synchronization. The default value is 50 (2 MB
per second).
The following table shows the relationship of the
rate value to the data copied per second.
Table 2. Relationship between the rate value
and the data copied per second| User-specified rate attribute value |
Data copied/sec |
|---|
| 1 - 10 |
128 KB |
| 11 - 20 |
256 KB |
| 21 - 30 |
512 KB |
| 31 - 40 |
1 MB |
| 41 - 50 |
2 MB |
| 51 - 60 |
4 MB |
| 61 - 70 |
8 MB |
| 71 - 80 |
16 MB |
| 81 - 90 |
32 MB |
| 91 - 100 |
64 MB |
- Create copies in synch
- Select
this option to create synchronized copies. Select this
option when MDisks are already formatted or when read stability to
unwritten areas of the VDisk is not required.
- Space-efficient
- Select this option to create a space-efficient
copy of the VDisk.
If you select this option, these additional options are available:
- Real size to initially allocate
- Specify the disk
space to be allocated for the space-efficient
copy of the selected VDisk. Setting the real space for a space-efficient
copy protects the copy from going offline when its MDisk group runs
out of space. You can either specify a percentage of the VDisk's capacity
for the copy or enter a specific amount of real capacity to allocate.
If you enter a specific amount you must also select the units for
the space. The following units can be selected:
- Warn when used capacity of VDisk reaches
- Specify
a threshold to send a warning message for the VDisk copy
when the capacity that is used first exceeds the specified level.
You can either specify a percentage of VDisk capacity or enter a
specific amount of capacity to be allocated. If you enter a specific
amount, you must also select the units for the space. The following
units can be selected:
If you select Autoexpand,
the default
value for the warning level is 80% of the virtual disk capacity. If Autoexpand is
not selected, the default value for the warning level is 80% of the
real capacity. To disable warnings, specify 0 or 0%.
- Autoexpand
- Select this option if you want the
space-efficient copies to automatically
expand their real capacities by allocating new extents from their
MDisk group.
- Grain size
- Select
the grain size in kilobytes (KB) for a space-efficient
copy of the VDisk. The following values are possible:
- Format the
new VDisk copy and mark the VDisk synchronized
- Select this
option to format the VDisk copy and synchronize the
copy with the primary copy of the VDisk.
- Image
- Select this
option to create the copy of the VDisk from one MDisk
that is not in an MDisk group. Provides a direct block-for-block translation
from the MDisk to the VDisk. Intended for MDisks that already contain
data that was not written through the SAN Volume Controller.
The following fields are available when
you select to add a image mode VDisk copy:
- Select
an MDisk to use for your Image copy
- Select the available unmanaged
MDisk that you can create a VDisk
copy from.
- Choose the managed disk group
from which physical space will be
used
- Select a MDisk group that extents will be used to create
the image
mode VDisk copy.
- Synchronization Rate
- Specifies the copy synchronization rate. A value
of zero (0) prevents synchronization. The default value is 50 (2 MB
per second).
The following table shows the relationship of the
rate value to the data copied per second.
Table 3. Relationship between the rate value
and the data copied per second| User-specified rate attribute value |
Data copied/sec |
|---|
| 1 - 10 |
128 KB |
| 11 - 20 |
256 KB |
| 21 - 30 |
512 KB |
| 31 - 40 |
1 MB |
| 41 - 50 |
2 MB |
| 51 - 60 |
4 MB |
| 61 - 70 |
8 MB |
| 71 - 80 |
16 MB |
| 81 - 90 |
32 MB |
| 91 - 100 |
64 MB |
- Create copies in
synch
- Select this option to create synchronized copies. Select
this
option when MDisks are already formatted or when read stability to
unwritten areas of the VDisk is not required.
- Space-efficient
- Select this option to create a space-efficient
copy of the VDisk.
If you select this option, these additional options are available:
- Real size to initially allocate
- Specify the disk
space to be allocated for the space-efficient
copy of the selected VDisk. Setting the real space for a space-efficient
copy protects the copy from going offline when its MDisk group runs
out of space. You can either specify a percentage of the VDisk's capacity
for the copy or enter a specific amount of real capacity to allocate.
If you enter a specific amount you must also select the units for
the space. The following units can be selected:
- Warn when used capacity of VDisk reaches
- Specify
a threshold to send a warning message for the VDisk copy
when the capacity that is used first exceeds the specified level.
You can either specify a percentage of VDisk capacity or enter a
specific amount of capacity to be allocated. If you enter a specific
amount, you must also select the units for the space. The following
units can be selected:
If you select Autoexpand,
the default
value for the warning level is 80% of the virtual disk capacity. If Autoexpand is
not selected, the default value for the warning level is 80% of the
real capacity. To disable warnings, specify 0 or 0%.
- Autoexpand
- Select this option if you want the
space-efficient copies to automatically
expand their real capacities by allocating new extents from their
MDisk group.
- Grain size
- Select
the grain size in kilobytes (KB) for a space-efficient
copy of the VDisk. The following values are possible:
- Format the
new VDisk copy and mark the VDisk synchronized
- Select this
option to format the VDisk copy and synchronize the
copy with the primary copy of the VDisk.
Actions
The
following actions are available:
- OK
- Click
this button to add a copy to a VDisk.
- Cancel
- Click this button to exit the panel without adding a copy to a
VDisk.