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302 DS8000 Series: Concepts and Architecture
This requires an adequate bandwidth for the connectivity between the disk storage servers to
the system image which hosts the SDMs. Because XRC in migration mode stores the data
through, it mainly requires channel bandwidth and SDM tends to monopolize its channels.
Therefore, the approach with dedicated channel resources is an advantage over a shared
channel configuration and would almost not impact the application I/Os.
XRC requires disk storage subsystems which support XRC primary volumes through the
microcode. Currently only IBM- or HDS-based controllers support XRC as a primary or
source disk subsystem. As an exception, this does not apply to the IBM RVA storage
controller, which does not support XRC as a primary XRC device. Also, EMC does not
provide XRC support at the XRC primary site.
14.2.3 Hardware- or microcode-based migration
Hardware- and microcode-based migration through remote copy is usually only possible
between like hardware, so using remote copy through microcode is not possible with different
disks from vendor A at the source site and disks from vendor B at the target site. Therefore,
we discuss only what is possible for IBM disk storage servers using remote copy or
Peer-to-Peer Remote Copy (PPRC) and its variations.
Remote copy approaches with Global Mirror, Metro Mirror, Metro/Global Copy, and Global
Copy allow the primary and secondary site to be any combination of ESS 750s, ESS 800s
and DS6000s or DS8000s.
Although IBM did not announce support of Metro/Global Copy for the DS8000, it will work for
certain migration scenarios, as outlined in the next section, when the DS8000 disk server
receives the data as the Global Copy secondary disk server. In this case the DS8000 holds
the Global Copy secondary volumes within a plain Global Copy relationship with the
respective ESS as the Global Copy primary disk server.
Bridge from ESCON to FICON with Metro/Global Copy
The ESS Model E20 and Model F20 do not support PPRC over Fibre Channel links, but only
PPRC based on PPRC ESCON links. In contrast, the newly announced disk storage servers
support only PPRC over Fibre Channel links and do not support PPRC ESCON links. The
ESS Model 800 supports both PPRC link technologies.
Figure 14-4 Intermediate ESS 800 used to migrate data with PPRC over ESCON from older models
Intermediate ESS 800
FICON
PPRC
Links
FCP
PPRC
Links
ESCON
ESS F20
ESCON
Global Copy
Metro Mirror
Cascading
Metro/Global Copy
DS8000
ESS F20