IBM System storage DS6000 Series, Redbook

Page: 239 / 578

Chapter 18. Global Copy options and configuration
215
18.7 Global Copy connectivity
Global Copy pairs are set up between volumes in LSSs, usually in different disk subsystems,
and these are normally in separate locations. A
path
(or group of paths) needs to be defined
between the source LSS and the target LSS. These
logical paths
are defined over
physical
links
between the disk subsystems.
The physical link includes the host adapter in the source DS6000, the cabling, switches or
directors, any wideband or long distance transport devices (DWDM, channel extenders,
WAN), and the host adapters in the target disk subsystem. Physical links can carry multiple
Global Copy logical paths, as shown in Figure 18-5.
Figure 18-5 Logical paths and physical links
Paths are
unidirectional
, that is, they are defined to operate in either one direction or the
other. Global Copy is
bidirectional
; that is, any particular pair of LSSs can have paths defined
among them that have opposite directions—each LSS holds both source and target volumes
from the other LSS. Moreover, opposite direction paths are allowed to be defined on the
same Fibre Channel physical link.
For bandwidth and redundancy, more than one path can be created between the same LSSs.
Global Copy will balance the workload across the available paths between the source and
target LSSs.
Physical links are bidirectional and can be shared by other Global Copy pairs as well as other
remote mirror and copy functions, such as Metro Mirror and Global Mirror.
18.7.1 Fibre Channel links
We recommend that you read the discussion presented in 13.4.1, “Fibre Channel links” on
page 143, in the Metro Mirror chapter, because it is also valid for Global Copy.
Note: For Global Copy, the DS6000 supports Fibre Channel links only. To facilitate ease of
testing, the DS6000 does support Global Copy source and target on the same DS6000.
Note: Remember that the LSS is not a physical construct in the DS6000; it is a logical con-
struct. Volumes in an LSS can come from multiple disk arrays.
Physical
Fiber Channel link
256 paths per
FCP link
LSS 00
LSS 03
LSS 01
LSS 02
LSS 1F
:
:
LSS 00
LSS 03
LSS 01
LSS 02
LSS 1F
:
: