Sandisk Corporation

Sandisk Technologies Inc.

Alan Douglas Bryce

Sergey Anatolievich Gorobets

Alan David Bennett

Carlos J Gonzalez

Alan Welsh Sinclair

Peter John Smith

In a nonvolatile memory with block management system, critical data such as control data for the block management system is maintained in duplicates. Various methods are described for robustly writing and reading two copies of critical data in multi-state memory. In another aspect of the invention, a preemptive garbage collection on memory block containing control data avoids an undesirable situation where a large number of such memory blocks need be garbage collected at the same time.

Non-volatile memory and method with control data management

The present invention presents techniques for the linking of physical blocks of a non-volatile memory into composite logical structures or 'metablocks'. After determining an initial linking of good physical blocks into metablocks, a record of the linking is maintained in the non-volatile memory where it can be readily accessed when needed. In one set of embodiments, the initially linking is deterministically formed according to an algorithm and can be optimized according to the pattern of any bad blocks in the memory. As additional bad blocks arise, the linking is updated using by replacing the bad blocks in a linking with good blocks, preferably in the same sub-array of the memory as the block that they are replacing.

Adaptive deterministic grouping of blocks into multi-block units

The present invention presents a number of improvements for managing erase processes in non-volatile memory. Such memory systems typically manage the memory by logically organize the basic unit of physical erase (erase block) into composite logical groupings (meta-blocks or logical group), where an erase block generally consists of a number of sectors. When an erase command is received, the specified sectors are checked against the memory system's control data. If the specified sectors span any full logical grouping, the full logical groupings can each be treated as a whole and erased according to one process (such as performing a true, physical erase), while other sectors are 'logically' erased at the sector level by standard techniques.

Structures for the management of erase operations in non-volatile memories

Methods for the management of erase operations in non-volatile memories

A non-volatile memory system is organized in physical groups of physical memory locations. Each physical group (metablock) is erasable as a unit and can be used to store a logical group of data. A memory management system allows for update of a logical group of data by allocating a metablock dedicated to recording the update data of the logical group. The update metablock records update data in the order received and has no restriction on whether the recording is in the correct logical order as originally stored (sequential) or not (chaotic). Eventually the update metablock is closed to further recording. One of several processes will take place, but will ultimately end up with a fully filled metablock in the correct order which replaces the original metablock. In the chaotic case, directory data is maintained in the non-volatile memory in a manner that is conducive to frequent updates. The system supports multiple logical groups being updated concurrently.

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Port Kennedy, Australia

Alan Douglas Bryce