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Appendix B. Using the DS6000 with iSeries 357
Based on available measurements and experiences with the ESS 800 we recommend you
should plan no more than four iSeries I/O adapters to one host port in the DS6000.
For a current list of switches supported under OS/400, refer to the iSeries Storage Web site
at:
http://www-1.ibm.com/servers/eserver/iseries/storage/storage_hw.html
Migration
For many iSeries customers, migrating to the DS6000 will be best achieved using traditional
Save/Restore techniques. However, there are some alternatives you may wish to consider.
OS/400 mirroring
Although it is possible to use OS/400 to mirror the current disks (either internal or external) to
a DS6000 and then remove the older disks from the iSeries configuration, this is not
recommended because both the source and target disks must initially be unprotected. If
moving from internal drives, these would normally be protected by RAID-5 and this protection
would need to be removed before being able to mirror the internal drives to the DS6000
logical volumes.
Once an external logical volume has been created, it will always keep its model type and be
either protected or unprotected. Therefore, once a logical volume has been defined as
unprotected to allow it to be the mirror target, it cannot be converted back to a protected
model and therefore will be a candidate for all future OS/400 mirroring, whether you want this
or not. See Table B-1 on page 330 for DS6000 logical volume models and types.
Metro Mirror and Global Copy
Depending on the existing configuration, it may be possible to use Metro Mirror or Global
Copy to migrate from an ESS to a DS6000 (or indeed, any combination of external storage
units which support Metro Mirror and Global Copy). For further discussion on Metro Mirror
and Global Copy, see 15.2.2, “Subsystem-based data migration” on page 295. Consider the
example shown in Figure B-35 on page 358.
Here, the iSeries has its internal Load Source Unit (LSU) and possibly some other internal
drives. The ESS provides additional storage capacity. Using Metro Mirror or Global Copy, it is
possible to create copies of the ESS logical volumes in the DS6000.
When ready to migrate from the ESS to the DS6000, you should do a complete shutdown of
the iSeries, unassign the ESS LUNs and assign the DS6000 LUNs to the iSeries. After IPLing
the iSeries, the new DS6000 LUNs will be recognized by OS/400, even though they are
different models and have different serial numbers.
Note: It is important to ensure that both the Metro Mirror or Global Copy source and target
copies are not assigned to the iSeries at the same time because this is an invalid
configuration. Careful planning and implementation is required to ensure this does not
happen, otherwise unpredictable results may occur.