Creating a FlashCopy mapping–Set properties

Fields

FlashCopy Mapping Name

Enter a name for the FlashCopy mapping. If you do not specify a name, the system automatically assigns a name in the form of fcmap<number>, where the <number> sequentially increases based on the names and numbers of current mappings.

Consistency Group Name

Select a consistency group to contain the new mapping. A consistency group is a group of mappings that can be started at the same time. With a consistency group, multiple virtual disks can be copied at the same time, which creates a consistent copy of multiple disks. If a consistency group is not selected, no value is set. If you specified the consistency group to be deleted automatically when it is empty, the consistency group is displayed with (autodelete) behind the name. A consistency group without automatic deletion specified is displayed with (non autodelete) behind the name.

Copy Rate (NOCOPY)

Select the copy rate. The value 1 is the lowest rate and 100 is the highest. Select NOCOPY to disable the copy. The default value is 50 (2 MB per second).

The following table shows the relationship of the copy and cleaning rate value to the attempted number of grains to be split per second. A grain is the unit of data represented by a single bit.

Table 1. Relationship between the rate, data rate and grains per second values

User-specified rate attribute value	Data copied/sec	256 KB grains/sec	64 KB grains/sec
1 - 10	128 KB	0.5	2
11 - 20	256 KB	1	4
21 - 30	512 KB	2	8
31 - 40	1 MB	4	16
41 - 50	2 MB	8	32
51 - 60	4 MB	16	64
61 - 70	8 MB	32	128
71 - 80	16 MB	64	256
81 - 90	32 MB	128	512
91 - 100	64 MB	256	1024

The data copied per second and the grains per second numbers represent standards that the SAN Volume Controller tries to achieve. The SAN Volume Controller is unable to achieve these standards if insufficient bandwidth is available from the nodes to the physical disks that make up the managed disks (MDisks) after taking into account the requirements of foreground I/O. If this situation occurs, background copy I/O contends for resources on an equal basis with I/O that arrives from hosts. Both tend to see an increase in latency and consequential reduction in throughput with respect to the situation had the bandwidth not been limited.

Cleaning Rate (NOCLEAN is the lowest rate)

Select the cleaning rate. The value NOCLEAN is the lowest rate and 100 is the highest. The default value is 50.

This clean rate minimizes the amount of time that a mapping is in the stopping state. See Table 1 for details.

Type

Select the type of FlashCopy mapping: Standard or Incremental. If you do not specify a value, the default value of Standard is used. A standard mapping includes the entire VDisk. An incremental mapping copies only the parts of the source or target VDisk that have changed since the last FlashCopy process. This reduces the amount of time that it takes to recreate an independent FlashCopy image.

Note: If the specified source and target VDisks are the target and source VDisks, respectively, of an existing mapping, then the mapping being created and the existing mapping become partners. If one mapping is created as incremental, then its partner is automatically incremental. A mapping can have only one partner.

Grain Size

Select either 64 KB or 256 KB as the grain size. If you do not specify a value, the default value of 256 is used.

The FlashCopy bitmap contains one bit for each grain. The bit records if the associated grain has been split by copying the grain from the source to the target.

Note: If you intend to use space-efficient VDisks in the FlashCopy mapping, you must match the grain size for performance reasons.

Automatically delete mapping when the background copy completes

Check this checkbox to automatically delete a FlashCopy mapping after the background copy has completed.

Actions

The following actions are available:

Back

Click this button to return to the previous panel.

Next

Click this button after you have completed this panel.

Cancel

Click this button to exit this wizard without creating a FlashCopy mapping.