182 IBM System Storage N series Hardware GuideSpare serversSome enterprises keep spare equipment around in case of failure. Generally, this is the mostexpensive solution and is only practical for the largest enterprises.An often overlooked similar situation is the installation of new servers. Additional orreplacement equipment is always being brought into most data environments. Bringing thisequipment in a bit early and using it as spare or test equipment is a good practice. Storageadministrators can practice new procedures and configurations, and test new softwarewithout having to do so on production equipment.Local clusteringThe decision to use the high availability features of IBM System Storage N series isdetermined by availability and service level agreements. These agreements affect the dataand applications that run on the IBM System Storage N series storage systems. If it isdetermined that a Active/Active configuration is needed, it affects sizing. Rather than sizingfor all data, applications, and clients serviced by one IBM System Storage N series node, theworkload is instead divided over two or more nodes.Failover performanceAnother aspect of a Active/Active configuration is failover performance. As an example, youhave determined that the data, application, or clients require constant availability of the IBMSystem Storage N series, and use Active/Active configurations. However, you might havesized for normal operations on each node and not failover. So what was originally a normalworkload for a single node has now doubled.You also must consider the service level agreement for response time, data access, andapplication performance. How long can your customers work within a degraded performanceenvironment? If the answer is not long at all, the initial sizing of each node also must takefailover workload into consideration. Because failover operation is infrequent and usuallyremedied quickly, it is difficult to justify these additional standby resources unless maintainingoptimum performance is critical. An example is a product ordering system with the datastorage or application on an IBM System Storage N series storage system. Any effect on theability to place an order affects sales.Software upgradesIBM regularly releases minor upgrades and patches for the Data ONTAP software. Lessfrequently there are also major release upgrades, such as version 8.1.You need to be aware of the new software versions for these reasons: Patches address recently corrected software flaws Minor upgrades will bundle multiple patches together, and might introduce new features Major upgrades generally introduce significant new featuresTo remain informed of new software releases, subscribe to the relevant sections at the IBMautomatic support notification website at:https://www.ibm.com/support/mynotificationsUpgrades for Data ONTAP, along with mechanisms for implementing the upgrade areavailable on the web at:http://www.ibm.com/storage/support/nasBe sure that you understand the recommendations from the vendor and the risks. Use all theavailable protection tools such as Snapshots and mirrors to provide a fallback in case the
