IBM Storwize V5030 User Manual

Chapter 10. Copy services 509
The
background copy rate is a property of a FlashCopy mapping that is defined as a value
0 - 100. The background copy rate can be defined and changed dynamically for individual
FlashCopy mappings. A value of 0 disables the background copy.
Table 10-5 shows the relationship of the background copy rate value to the attempted number
of grains to be copied per second.
Table 10-5 Background copy rate
The grains per second numbers represent the maximum number of grains that the IBM
Storwize V5000 copies per second, assuming that the bandwidth to the managed disks
(MDisks) can accommodate this rate.
If the IBM Storwize V5000 Gen2 system 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 make progress, and do not stop, hang, or
cause the node to fail. The background copy is performed by both nodes of the I/O Group in
which the source volume is found.
10.3.14 Serialization of I/O by FlashCopy
In general, the FlashCopy function in the IBM Spectrum Virtualize introduces no explicit
serialization into the I/O path. Therefore, many concurrent I/Os are allowed to the source and
target volumes.
Value Data copied per
second
Grains per second
(256 KB grain)
Grains per second
(64 KB grain)
01 - 10 128 KiB 0,000.5 00,002
11 - 20 256 KiB 0,001 00,004
21 - 30 512 KiB 0,002 00,008
31 - 40 001 mebibyte (MiB) 0,004 00,016
41 - 50 002 MiB 0,008 00,032
51 - 60 004 MiB 0,016 00,064
61 - 70 008 MiB 0,032 00,128
71 - 80 016 MiB 0,064 00,256
81 - 90 032 MiB 0,128 00,512
91 - 100 064 MiB 0,256 01,024
101 - 110 128 MiB 0,512 02,048
111 - 120 256 MiB 1,024 04,096
121 - 130 512 MiB 2,048 08,192
131 - 140 1 GiB 4,096 16,384
141 - 150 2 GiB 8,192 32,768

IBM Storwize V5030 Specifications

General

Brand	IBM
Model	Storwize V5030
Category	Storage
Language	English