IBM DS8000 - ADDITIONAL INFORMATION, User Manual, Page: 162 / 250

There are two types of LUN protection: protected and unprotected. In reality, both
volume protection types have the same DS8000 internal RAID protection. If you
define a LUN as protected, it is protected by the hardware (the DS8000) rather
than by i5/OS host-based mirroring. If you define a LUN as unprotected, either
the i5/OS or another LUN of equal capacity, either internally or externally mirrors
it. The unprotected type is typically used for Load Source Unit mirroring. (Each
System i or LPAR partition has a special disk called the Load Source Unit. It holds
the system’s microcode and is used to reboot the system.) Unless you intend to use
i5/OS (host based) mirroring, you should define your LUNs as protected.
In addition, i5/OS supports multipathing, which is part of the base operating
system. Multipathing provides redundant path solutions for System i but is only
used for external storage like the DS8000. Each connection for a multipath disk
unit functions independently. Several connections provide availability by allowing
disk storage to be used even if a single path fails.
Some i5/OS considerations are similar to other operating systems regarding how
LUNs are defined to volume groups. For example, to access volumes for Copy
Services functions with i5/OS, a separate volume group for the target volume IDs
is required. Because you do not want to write to the target volumes from the same
host while Copy Services functions are running, you might want to put the target
volumes in an unassigned volume group until the volumes are needed.
Assuming that you have set up and configured your DS8000 for i5/OS, you can
perform FlashCopy and remote mirror and copy operations to create copies of
System i disk pools within a single DS8000 or to a distant DS8000 using remote
mirror and copy functions. You can save this data and back it up to tape.
You can install and run the DS CLI on i5/OS to allow you to perform Copy
Services functions that are supported on the DS8000. You can also use the DS
Storage Manager for i5/OS to perform Copy Services functions. The size of the
target volumes must be equal the size of the corresponding source volumes. Any
mismatch causes the task to fail.
System i Copy Services Toolkits
The System i Copy Services Toolkit allows you to use the data mirroring
capabilities of Copy Services functions on the DS8000. The Toolkit allows you to
take advantage of these functions with minimal downtime of your production
system. The Toolkit interfaces with the DS CLI and DS Storage Manager to send
Copy Services commands to the DS8000. For more information about the Toolkit,
contact your IBM representative.
FlashCopy with the System i Copy Services Toolkit
Once configured and implemented, the Toolkit will manage all of the
System i functions that are necessary to use FlashCopy, which can involve
creating a point-in-time version of an independent disk pool called an
independent auxiliary storage pool (IASP).
Note: In a System i environment, disk pools are included in auxiliary
storage pools (ASPs). Data is scattered across all disks in a given
ASP. The first ASP on the system is called the System ASP and
includes the operating system. Users can optionally have additional
ASPs called user ASPs. These are typically used to hold database
journals and savefiles, since these objects need to be separated from
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DS8000 User’s Guide