SOLID STATE DEVICE PARITY CACHING IN A HYBRID STORAGE ARRAY

摘要

A storage manager can reduce the overhead of parity based fault tolerance by leveraging the access performance of SSDs for the parities. Since reading a parity value can be considered a small read operation, the reading of parity from an SSD is an effectively "free" operation due to the substantially greater SSD read performance. With reading parity being an effectively free operation, placing parity on SSDs eliminates the parity read operations (in terms of time) from the parity based fault tolerance overhead. A storage manager can selectively place parity on SSDs from HDDs based on a criterion or criteria, which can relate to frequency of access to the data corresponding to the parity. The caching criterion can be defined to ensure the reduced overhead gained by reading parity values from a SSD outweighs any costs (e.g., SSD write endurance).