What are the two conditions that trigger a consistency point (CP)?

A consistency point (CP) is a crucial event that ensures data integrity within a storage system. It serves as a snapshot of the data at a specific moment in time, allowing the system to maintain a consistent state even in the event of failures or interruptions. The two primary conditions that trigger a CP are tied to system performance and data protection mechanisms.

When the 10-second timer expires, it indicates a regular cadence of consistency checks within the system. This timer ensures that the system frequently creates checkpoints to safeguard data, thereby minimizing the risk of data loss during sudden events like power outages or crashes. Similarly, when the NVRAM (Non-Volatile Random Access Memory) buffer fills up, it prompts the system to clear and commit the buffered writes to persistent storage. This action triggers a CP to ensure that all buffered changes are accurately recorded and the state of the storage environment reflects all recent transactions.

These conditions are fundamental to maintaining the reliability and consistency of the storage system’s data, ensuring that it can be restored to a known good state should the need arise. The other options relate either to maintenance activities or manual tasks that do not directly induce the automatic, system-level data integrity assurance provided by a CP.