Abstract: Methods and apparatus for writing data to non-volatile memory include maintaining one or more lists of obsolete blocks of the non-volatile memory and limiting the lists to a predetermined value. If a write operation would result in a list exceeding its predetermined value, a block erase operation is performed on one of the obsolete blocks. Valid data contained in an obsolete block selected for erasure is relocated prior to erasure.

Abstract: Update data to a non-volatile memory may be recorded in at least two interleaving streams such as either into an update block or a scratch pad block depending on a predetermined condition. The scratch pad block is used to buffered update data that are ultimately destined for the update block. In a preferred embodiment, an index of the data stored in the scratch pad block as well that stored in the update block is saved in an unused portion of the scratch pad block every time the scratch pad block is written to.

Abstract: Update data to a non-volatile memory may be recorded in at least two interleaving streams such as either into an update block or a scratch pad block depending on a predetermined condition. The scratch pad block is used to buffered update data that are ultimately destined for the update block. Synchronization information about the order recording of updates among the streams is saved with at least one of the streams. This will allow the most recently written version of data that may exist on multiple memory blocks to be identified. In one embodiment, the synchronization information is saved in a first block and is a write pointer that points to the next recording location in a second block. In another embodiment, the synchronization information is a time stamp.

Abstract: In a nonvolatile memory with a block management system, data written to blocks include host write data and also system control data for managing the blocks. When a block is full or no longer accepting data, it is closed after valid versions of the data on it are relocated to another block in a rewrite operation. An improved pre-emptive rewrite scheme prevents a worst-case situation where multiple rewrites to occur at once when they happened to be full at the same time. Particularly, the scheduling of the pre-emptive rewrites for control data is based on a number of considerations including the time required for each control block rewrite and the time available for control block rewrites based on the configuration of the update blocks for storing host data, the time required in the foreground host operation and the host write latency.

Abstract: In a nonvolatile memory with a block management system, data written to blocks include host write data and also system control data for managing the blocks. When a block is full or no longer accepting data, it is closed after valid versions of the data on it are relocated to another block in a rewrite operation. An improved pre-emptive rewrite scheme prevents a worst-case situation where multiple rewrites to occur at once when they happened to be full at the same time. Particularly, the scheduling of the pre-emptive rewrites for control data is based on a number of considerations including the time required for each control block rewrite and the time available for control block rewrites based on the configuration of the update blocks for storing host data, the time required in the foreground host operation and the host write latency.

Abstract: According to a first aspect of the invention, there is provided a controller connected to a non-volatile memory and including a volatile memory, wherein the controller maintains lists in volatile memory of blocks in the non-volatile memory allocated for storage of logical sector data and of blocks recently erased in the non-volatile memory.

Abstract: In a memory array having a minimum unit of erase of a block, a scratch pad block is used to store data that is later written to another block. The data may be written to the scratch pad block with a low degree of parallelism and later written to another location with a high degree of parallelism so that it is stored with high density. Data may be temporarily stored in the scratch pad block until it can be more efficiently stored elsewhere. This may be when some other data is received. Unrelated data may be stored in the same page of a scratch pad block.

Abstract: A re-programmable non-volatile memory system, such as a flash EEPROM system, having its memory cells grouped into blocks of cells that are simultaneously erasable is operated to perform memory system housekeeping operations in the foreground during execution of a host command, wherein the housekeeping operations are unrelated to execution of the host command. Both one or more such housekeeping operations and execution of the host command are performed within a time budget established for executing that particular command. One such command is to write data being received to the memory. One such housekeeping operation is to level out the wear of the individual blocks that accumulates through repetitive erasing and re-programming.

Abstract: 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.

Abstract: 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.

Abstract: According to a first aspect of the invention, there is provided a controller connected to a non-volatile memory and including a volatile memory, wherein the controller maintains lists in volatile memory of blocks in the non-volatile memory allocated for storage of logical sector data and of blocks recently erased in the non- volatile memory.