Abstract: A technique processes input/output (I/O) requests from a set of host computers. The technique utilizes data storage equipment which includes a set of physical storage drives and storage processing circuitry which accesses the set of physical storage drives. The technique involves storing, by the storage processing circuitry, a set of storage drive objects in main memory. The set of storage drive objects includes a set of zeroed chunk tables. Each storage drive object (i) represents a physical storage drive and (ii) includes a zeroed chunk table which identifies storage chunks of that physical storage drive that have been initialized to zero. The technique further involves receiving, by the storage processing circuitry, I/O requests from the set of host computers, and performing, by the storage processing circuitry, I/O tasks in response to the I/O requests. The I/O tasks include zero on demand operations based on the set of zeroed chunk tables.

Abstract: A method is used in managing data availability in storage systems. A request to write new data to a disk of a plurality of disks of a data storage system is received. The plurality of disks includes first and second parity areas. The first parity area includes first parity information and the second parity area includes second parity information. Up to two disks of the plurality of disks are having a problem. Old data of the disk is reconstructed in a memory of the data storage system. The reconstructed old data of the disk is written to a parity area. The parity area is selected from the first or second parity areas based on a configuration preference. The new data is written to the parity area.