International Business Machines Corporation

Werner K Bux

Robert Haas

Roman Alexander Pletka

Ilias Iliadis

Xiao-Yu Hu

Pitro A Zafiropulo

Erwin A Zurfluh

Mehdi M Nassehi

Hans R Mueller

Johann R Muller

Xiao-yu Hu

Harmen R Van As

Johann R Mueller

Ernst H Rothauser

Felix H Closs

Roy C Dixon

Heinrich J Keller

The present idea provides a high read and write performance from/to a solid state memory device. The main memory of the controller is not blocked by a complete address mapping table covering the entire memory device. Instead such table is stored in the memory device itself, and only selected portions of address mapping information are buffered in the main memory in a read cache and a write cache. A separation of the read cache from the write cache enables an address mapping entry being evictable from the read cache without the need to update the related flash memory page storing such entry in the flash memory device. By this design, the read cache may advantageously be stored on a DRAM even without power down protection, while the write cache may preferably be implemented in nonvolatile or other fail-safe memory. This leads to a reduction of the overall provisioning of nonvolatile or fail-safe memory and to an improved scalability and performance.

Logical to physical address mapping in storage systems comprising solid state memory devices

An apparatus and method for a memory controller for managing scheduling requests in a solid state memory device. The memory includes a set of units wherein a unit within the set of units is erasable as a whole by a unit reclaiming process resulting in a free unit available for writing data to. The memory controller further includes a first queue for queuing user requests for reading and/or writing data from/to the memory, and a second queue for queuing unit reclaiming requests for executing the unit reclaiming process. A scheduler is provided for selecting user requests from the first queue and unit reclaiming requests from the second queue for execution according to a defined ratio. The defined ratio is a variable ratio, is dependent on the current number of free units, and permits the memory controller to select requests from both the first queue and the second queue.

Scheduling requests in a solid state memory device

A method for garbage collection in a solid state drive (SSD) includes determining whether the SSD is idle by a garbage collection module of the SSD; based on determining that the SSD is idle, determining a victim block from a plurality of memory blocks of the SSD; determining a number of valid pages in the victim block; comparing the determined number of valid pages in the victim block to a valid page threshold; and based on the number of valid pages in the victim block being less than the valid page threshold, issuing a garbage collection request for the victim block.

Valid page threshold based garbage collection for solid state drive

A protocol and format for multiple accessing and transporting information in a Distributed Queue Dual Bus communications network includes count field in which stations can reserve multiple time slots for transporting data.

Method and apparatus for distributed queue multiple access in a

A distributed queue multiple access technique is disclosed for a system comprising two counterflowing transmission busses (A,B), plural stations (i, j) connected between them, and a headend station generating slots on the first one (A) of the busses; each station transmitting access requests on the second one (B) of the busses and determining its right to transmit data in slots on the first bus on the basis of access requests it has seen. Each station maintains a FIFO queue (41) for sequential storage of numbers representing external (EXT-REQ) and local (LOC-REQ) access requests. To achieve correct timing between access requests entering the queue from the second bus and respective free slots passing a station on the first bus, a station-individual delay is introduced by maintaining in a FIFO delay storage (71) a specific number of entries. This results in an equally fair treatment for all stations, and guarantees the availability of consecutive free slots for any station which requested them.

In a local area communication system comprising token rings (11) with synchronous bandwidth managers SBM (15) for issuing priority tokens for quasi-synchronous frames at regular intervals, the rings are interconnected by a time division muliplex PBX unit (21) via their SMB units. Buffers are provided in each SBM for synchronous information blocks transferred from and to the ring, and the TDM control (31) can independently access these buffers for TDM switching of the individual bytes of said information blocks. Besides this PBX interconnection for synchronous information or voice, the rings are also interconnected by a backbone bus or ring for transfer of asynchronous data between rings. A special slot rearrangement procedure is provided to improve the filling of time slots in the quasi-synchronous frames that are no longer used after release of a connection, to allow for adapting the frame length (number of issued slots) to the number of existing connections.

Local area communication system for integrated services based on a

In a network of communication rings (R1 . . . R7, BB) interconnected by bridges (B1 . . . B4), access to each ring is regulated by a circulating token which is normally issued at irregular intervals depending on occurrence and length of messages. To enable communication of messages which have to be transmitted synchronously, i.e., at regular intervals, each ring has a synchronous bandwidth manager SBM which periodically issues a token for only synchronous information. Each SBM is located in a bridge node (13, 15) but only one of them which is located in a particular bridge node (15) is the master SBM from which all other SBM's are synchronized, using a synchronous token and/or special synchronization circuitry in each bridge. This allows a common period in the whole network for handling synchronous information, even if all rings have different bit rates.

Synchronization in a communication network of interconnected rings

In a local communication network, stations can be attached via extension lines and individual ports in distribution panels to the main transmission ring (11). Each port has a physical address or local identification key. Means are provided for inserting the local key of a port into a station when it is plugged into the extension lines. Each station comprises units (33, 45) for generating a key demand signal and an idling signal pattern which are transmitted to the port, and a key register (47) for recording the key when it is received. Each port includes a read-only store and timing unit (41) which furnishes the local key in response to the received idling pattern which is converted to a clock signal. A switch (37) in the port is activated by a switch control unit (35) to insert the read-only store and timing unit into a wrap-around loop interconnecting input and output paths of the station.

Method and arrangement for local address acquisition by a station in a

In a ring communication system comprising several stations, access to the ring is granted to one station at a time by a circulating token indication. A method is provided guaranteeing a transmission opportunity for synchronous or circuit-switched data in periodic time intervals to authorized stations. A CS monitor station issues a frame header which is marked in a specific bit position to allow only authorized stations to transmit their synchronous data together with a distination address. In a first embodiment, a single frame comprises a plurality of slots each having a free/busy indication, a destination address field and a field for synchronous data, and each authorized station can occupy one such slot. In a second embodiment, a marked frame can be used by only one authorized station for transmitting synchronous data, but a new marked frame header is reissued until all authorized stations around the ring have transmitted synchronous data.

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Richterswil, Switzerland

Werner K Bux