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PowerMax arrays include enhancements that improve reliability, availability, and serviceability. This makes PowerMax arrays ideal choices for critical applications and 24x7 environments demanding uninterrupted access to information.
PowerMax array components have a mean time between failure (MTBF) of several hundred thousand to millions of hours for a minimal component failure rate. A redundant design allows systems to remain online and operational during component replacement. All critical components are fully redundant, including director boards, global memory, internal data paths, power supplies, battery backup, and all NVMe back-end components. Periodically, the system tests all components. PowerMaxOS reports errors and environmental conditions to the host system and to the Customer Support Center.
PowerMaxOS validates the integrity of data at every possible point during the lifetime of the data. From the point at which data enters an array, the data is continuously protected by error detection metadata, data redundancy, and data persistence. This protection metadata is checked by hardware and software mechanisms anytime data is moved within the subsystem, allowing the array to provide true end-to-end integrity checking and protection against hardware or software faults. Data redundancy and persistence allows recovery of data where the integrity checks fail.
The protection metadata is appended to the data stream and contains information describing the expected data location and CRC representation of the actual data contents. The expected values found in protection metadata are stored persistently in an area separate from the data stream. The protection metadata is used to validate the logical correctness of data being moved within the array anytime the data transitions between protocol chips, internal buffers, internal data fabric endpoints, system cache, and system disks.
PowerMaxOS supports industry standard T10 Data Integrity Field (DIF) block cyclic redundancy code (CRC) for track formats. For open systems, this enables a host generated DIF CRC to be stored with user data and used for end-to-end data integrity validation. Additional protections for address or control fault modes provide increased levels of protection against faults. These protections are defined in user-definable blocks supported by the T10 standard. Address and write status information is stored in the extra bytes in the application tag and reference tag portion of the block CRC.
The objective of this technical note is to provide an overview of the architecture of PowerMax arrays and the reliability, availability, and serviceability (RAS) features within PowerMaxOS.