Power supplies fail rarely. A failure often is the result of a problem with a breaker or a loose power cable.  Each RPC supplies power to the disk enclosures, management switch, and hosts. Replacing an RPC or  PDU requires a two-hour system outage. Failure cheat sheet The types of failures and their effect on the system are listed in Table 1. Failure type Effect Result Failure causes outage No Replacement needs outage No Impact on performance 60% lower until regeneration finishes Disk Criticality Minor Failure causes outage Yes Replacement needs outage Only 15 minutes after replacement is completed Impact on performance None (unless an IBM PureData System for  Analytics N2001-002, N2002-002, or N3001-002  system is used) SPU Criticality Minor Failure causes outage No Replacement needs outage No Impact on performance Up to 50% ESM Criticality Moderate Failure causes outage No Replacement needs outage No Impact on performance None Disk enclosure power supply Criticality Minor Failure causes outage No Replacement needs outage No Impact on performance None IBM BladeCenter power supply Criticality Minor Failure causes outage No Replacement needs outage No Impact on performance None IBM BladeCenter blower Criticality Moderate IBM BladeCenter gig switch Failure causes outage Yes (but not always) Replacement needs outage Yes (three hours) Impact on performance Up to 50% Criticality Moderate Management switch Failure causes outage No (but system cannot start) Replacement needs outage Yes Impact on performance None Criticality Critical Table 1 Failure cheat sheet Assessing Hardware Failures on IBM PureData System for Analytics N2001, N2002, and N3001 6