8456ch_RAS.fm Draft Document for Review January 13, 2020 5:02 pm GLYPH<SM590000> Each RPC card has two firmware images. If an RPC firmware update fails, the RPC card  can still boot from the other firmware image. This design also leads to a reduced period  during which one of the RPC cards is unavailable because of an RPC firmware update.  Because of the dual firmware image, an RPC card is only unavailable for the time that is  required (only a few seconds) to boot from the new firmware image after it is downloaded.  Because of this configuration, full RPC redundancy is available during most of the time  that is required for an RPC firmware update. GLYPH<SM590000> The RPC cards monitors power to the attached I/O enclosures. They also monitor  environmental components such as power, fans, and temperature for the I/O enclosures.  Environmental critical and noncritical conditions can generate EPOW events. Critical  events trigger the correct signals from the hardware to the affected components to prevent  any data loss without operating system or firmware involvement. Non-critical  environmental events are also logged and reported. 3.6.2 Line power loss 3.6.3 Line power fluctuation 3.6.4 Power control The DS8900F uses an area of server memory as NVS. This area of memory is used to hold  modified data that is not yet written to the storage drives. If line power fails, meaning that both  power domain report a loss of AC input power, the DS8900F must protect that data. For a full  explanation of the NVS and cache operation, see 3.2, “CPC failover and failback” on page 72 . If a power fluctuation occurs that causes a momentary interruption to power (often called a brownout ), the DS8900F tolerates this condition for approximately 20ms. If this is exceeded,  the flash enclosure, CPC and other components are powered off. Independent of this, the  NVDIMMs backed by the BPMs begin copying the contents of NVS to the flash memory to  hold the write cache data persistently for the next power on for destaging. For many clients  who use uninterruptible power supply (UPS) technology, brownouts are not an issue.  UPS-regulated power is reliable, so more redundancy in the attached devices is often  unnecessary. Power control is modified through the HMC, which communicates sequencing information to  the service processor in each CPC, RPC and iPDUs. Power control of the DS8900F can be  performed by using the Service Maintenance Console Web User Interface (WUI) or by using  the DS8900F Storage Management GUI or DS CLI commands. Figure 3-9 on page 94 shows the Power Control in the Actions menu on the Dashboard of the  Storage Management GUI.  Figure 3-9 DS8900F Power control in the Storage Management GUI  94  IBM DS8900F Architecture and Implementation