448 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
The background copy rate property determines the speed at which grains are copied as a 
background operation, immediately after the FlashCopy mapping is started. That speed is 
defined by the user when creating the FlashCopy mapping, and can be changed dynamically 
for each individual mapping, whatever its state. Mapping copy rate values can be 0 - 150, with 
the corresponding speeds that are listed in Table 11-1.
When the background copy function is not performed (copy rate = 0), the target volume 
remains a valid copy of the source data only while the FlashCopy mapping remains in place. 
Table 11-1   Copy rate values
The grains per second numbers represent the maximum number of grains that the Storwize 
V7000 copies per second. This amount assumes that the bandwidth to the managed disks 
(MDisks) can accommodate this rate.
If the Storwize V7000 cannot achieve these copy rates because of insufficient width from the 
nodes to the MDisks, the background copy I/O contends for resources on an equal basis with 
the I/O that is arriving from the hosts. Background copy I/O and I/O that is arriving from the 
hosts tend to see an increase in latency and a consequential reduction in throughput.
Background copy and foreground I/O continue to progress, and do not stop, hang, or cause 
the node to fail.
The background copy is performed by one of the nodes that belong to the I/O group in which 
the source volume resides. This responsibility is moved to the other node in the I/O group if 
the node that performs the background and stopping copy fails.
User-specified copy rate attribute 
value 
Data 
copied/sec
256 KB 
grains/sec
64 KB 
grains/sec
1 - 10 128 KiB 0.5 2
11 - 20 256 KiB 1 4
21 - 30 512 KiB 2 8
31 - 40 1 MiB 4 16
41 - 50 2 MiB 8 32
51 - 60 4 MiB 16 64
61 - 70 8 MiB 32 128
71 - 80 16 MiB 64 256
81 - 90 32 MiB 128 512
91 - 100 64 MiB 256 1024
101 - 110 128 MiB 512 2048
111 - 120 256 MiB 1024 4096
121 - 130 512 MiB 2048 8192
131 - 140 1 GiB 4096 16384
141 - 150 2 GiB 8192 32768