6.1.1 SnapOPC+ Copy Destination Volume

If the physical capacity of the copy destination volume is insufficient, you cannot access the copy destination volume. Because of that, after estimating the physical capacity required for the copy destination volume according to the following procedure, create the copy destination volume.

Estimated Required Capacity for Copy Destination Volumes

The formula to estimate the physical capacity required for the SnapOPC+ copy destination volume is shown below.

Physical capacity = (number of updated blocks for the copy source volume) * (safety factor)

Strictly speaking, both the number of blocks that have been updated on the copy destination volume and the management area used by the hardware (about 0.1% of the logical capacity) should also be taken into consideration before SnapOPC+ is performed. However, this can be covered by increasing the safety factor.

For the update amount produced in the copy source volume, measure using the following procedure:

Start the estimation of the update amount by configuring a monitor session on the copy source volume.
[Execution example]
```
> acsnap start -estimate -v ET001/0x1
Successful completion
```
Start transactions. Blocks that are updated by transactions are recorded on the hardware.
After the estimation period has elapsed, check the number of blocks that have been updated.
[Execution example]
```
> acsnap query -estimate -v ET001/0x1
Update
------
   10M
```
After the estimation is completed, cancel the monitor session.
[Execution example]
```
> acsnap cancel -estimate -v ET001/0x1
```

Point

If an advance estimation is difficult, it is recommended that the physical capacity of the copy destination volume is 30 to 50 % of the total capacity of the copy source. As this is a recommended value, you must adjust according to the operational status.

See

Refer to "Chapter 4 Command References" for information on the commands.

Creating of Copy Destination Disk

To create a copy destination disk, use Storage Cruiser or ETERNUS Web GUI.

Point

Make logical space on a copy destination volume equal to that on a copy source volume.
Consider a disk expansion from the required physical capacity in the copy destination volume.
- If TPV is used as the copy destination volume
  Use Storage Cruiser or ETERNUS Web GUI to check the status of the Thin Provisioning Pool and expand the capacity of the Thin Provisioning Pool.
  For the operation procedure when using Storage Cruiser, refer to "Display Thin Provisioning Pool" and "Expand Capacity of/Format/Change Threshold Value of/Delete Thin Provisioning Pool" in the Web Console Guide.
- If FTV is used as the copy destination volume
  Use Storage Cruiser or ETERNUS Web GUI to check the status of the Tier pool and expand the sub-pool capacity of the Tier pool.
  For the operation procedure when using Storage Cruiser, refer to "Display Tier Pool" and "Expand Capacity of Sub-Pool in Tier Pool" in the Web Console Guide.
- If SDV is used as the copy destination volume
  Use the acsdv poolstat command or ETERNUS Web GUI to check the status of the SDP and expand the SDP capacity.
  Creating an exclusive volume named Snap Data Pool Volume (SDPV) enables the SDP and the created SDPV is automatically incorporated in the SDP. Creating an SDPV of the physical capacity that is assigned to a copy destination volume expands the SDP capacity.
  The operation procedure when using the acsdv poolstat command is as follows:
  1. Execute the acsdv poolstat command and check the status of the SDP.
  2. Create the SDPV with ETERNUS Web GUI.
If you use an SDV as the copy destination volume, initialize the SDV. To avoid wasting the physical space of the SDV, limit the creation of file systems to the minimum requirement for the update after initializing the SDV.

See

Refer to "Create Volume" in the Web Console Guide for information on how to create TPV/SDV/SDPV using Storage Cruiser. Refer to "Create FTV" in the Web Console Guide for information on how to create FTV.