IBM N series Hardware Manual page 221

You also must consider the service level agreement for response time, data access, and
application performance. How long can your customers work within a degraded performance
environment? If the answer is not long at all, the initial sizing of each node also must take
failover workload into consideration. Because failover operation is infrequent and usually
remedied quickly, it is difficult to justify these other standby resources unless maintaining
optimum performance is critical. An example is a product ordering system with the data
storage or application on an IBM System Storage N series storage system. Any effect on the
ability to place an order affects sales.
Software upgrades
IBM regularly releases minor upgrades and patches for the Data ONTAP software. Less
frequently there are also major release upgrades, such as version 8.1.
You need to be aware of the new software versions for the following reasons:
Patches address recently corrected software flaws.
Minor upgrades bundle multiple patches together and might introduce new features.
Major upgrades generally introduce significant new features.
To remain informed of new software releases, subscribe to the relevant sections at the
following IBM automatic support notification website:
https://www.ibm.com/support/mynotifications
Upgrades for Data ONTAP and mechanisms for implementing the upgrade are available at
this website:
http://www.ibm.com/storage/support/nas
Be sure that you understand the recommendations from the vendor and the risks. Use all the
available protection tools, such as Snapshots and mirrors, to provide a fallback in case the
upgrade introduces more problems than it solves. Whenever possible, perform incremental
unit tests on an upgrade before putting an upgrade into critical production.
Testing
As storage environments become ever more complex and critical, the need for
customer-specific testing increases in importance. Work with your storage vendors to
determine an appropriate and cost-effective approach to testing solutions to ensure that your
storage configurations are running optimally.
Even more important is that testing of disaster recovery procedures become a regular and
ingrained process for everyone that is involved with storage management.
Chapter 14. Designing an N series solution
201