Moving sectors within a block of information in a flash memory mass storage architecture

In a storage device for use with a host, the storage device having a controller and one or more flash memory devices, a method for accessing information within the flash memory devices under the direction of the controller, the information organized in sectors with one or more sectors defining a block wherein each block is selectively erasable having associated therewith an LBA (Logical Block Address) provided by the host and a PBA (Physical Block Address) developed by the controller for identifying an unused location within the flash memory devices wherein a sector may be stored, the method comprising:

• (a) allocating a table within the controller defined by rows, each row being individually addressable by an LBA and configured to store a virtual PBA, a moved virtual PBA, and status information for use in determining the location of a sector that has been moved from the virtual PBA to the moved virtual PBA within the flash memory devices;
• (b) providing to the controller, a particular LBA identifying a block being accessed by the host;
• (c) developing a PBA in association with the particular LBA;
• (d) using the particular LBA to address an LBA row;
• (e) storing the PBA associated with the particular LBA in the addressed LBA row;
• (f) upon further access of the block identified by the particular LBA, developing a moved virtual PBA;
• (g) storing the moved virtual PBA in the addressed LBA row;
• and
• (h) modifying the status information of the addressed LBA row to indicate whether any sectors within the addressed LBA row have been moved;
• wherein sectors of a block are moved to unused locations within the flash memory devices to avoid erase-before-write operations each time the block is accessed.

A controller device coupled to a host for storing information in nonvolatile memory, the information being organized in blocks with each block having associated therewith a logical block address (LBA) and a physical block address (PBA), the LBA being provided by the host to the controller device for identifying a block to be accessed, the PBA being developed by the controller device for identifying a location within the nonvolatile memory wherein the accessed block is to be stored, a stored block within the nonvolatile memory being selectively erasable and further having one or more sectors, comprising:

• a. a memory device for storing a table defined by n LBA rows, each of the LBA rows being uniquely addressable by an LBA and for storing a virtual PBA for identifying a first location for storing a block within the nonvolatile memory, a move virtual PBA for identifying a second location for storing one or more sectors of the stored block within the nonvolatile memory, and status information including a flag for indicating whether any sectors of the stored block have been moved to the move virtual PBA location within the nonvolatile memory;
• b. controller means responsive to a command from the host and operative to store a block of information in the nonvolatile memory, the block being identified by a particular LBA, said controller being operative to develop a virtual PBA if the particular LBA is "unused" and to develop a move virtual PBA if the particular LBA is "used",
• whereby said controller stores an LBA-identified block that may be accessed more than once by the host prior to erasure thereof, in more than one PBA-identified location within the nonvolatile memory thereby avoiding an erase operation each time the host writes to the controller device and avoiding transfer of an entire block to another location within the nonvolatile memory each time a portion of the block is re-written.