Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism
Reexamination Certificate
2001-10-25
2004-09-21
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Reexamination Certificate
active
06795264
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to the art of peripheral storage devices and, more particularly, to buffer management systems and methodologies for peripheral storage devices.
BACKGROUND OF THE INVENTION
Hard disk drives and other peripheral storage devices are standard features in most computer systems. Such devices provide mass storage functionality for a host computer, and may include hard disk drives, CDROM drives, tape drives, optical disk memory devices, floppy disk drives, and the like. Hard disk drives, for example, typically include one or more magnetically coated platters used for storing program instructions, data, and other information used by the computer system. One or more such platters may be configured in a stack, which is rotated by a spindle or servo motor. A space is provided between each platter to allow an arm having a read/write head to be positioned on each side of each platter such that information may be stored and retrieved. Information may be stored on one or both sides of the platters, which are generally organized into sectors, tracks, zones, and cylinders. The read/write heads are mounted onto one or more suspension arms whereby each of the read/write heads may be positioned as desired. The suspension arms are coupled together at a voice coil motor (VCM) to form one positionable unit or assembly. The VCM positions the suspension arms so that an active read/write head is properly positioned for reading or writing information. The read/write heads may thus be positioned between an inner diameter and an outer diameter of the platters in a controlled fashion to access data stored thereon.
Hard disk drives and other types of peripheral storage devices also include a variety of electronic control circuitry for processing data and for controlling its overall operation, including a hard disk controller. Typical controllers include a processor, a pre-amplifier, a read channel, a write channel, a servo controller, a motor control circuit, a read-only memory (ROM), a random-access memory (RAM), and a variety of disk control circuitry to control the operation of the hard disk drive and to properly interface the hard disk drive to a bus in a host computer system. The disk control circuitry generally includes a processor (e.g., a DSP, microprocessor, microcontroller, or the like) for executing instructions stored in memory to control the operation and interface of the hard disk drive.
Hard disk drives and other peripheral storage devices perform write, read, and servo operations when storing and retrieving data. Generally, a write operation includes receiving data from a system bus and storing the data on the platters. In a read operation, the appropriate sector to be read is located and data that has been previously written to one or more platters is read. The data is then provided to the host computer system. Modern peripheral storage devices include some form of buffer memory, usually segmented, to buffer or temporarily store information on its way from the host system to the storage media (platters) and/or on its way from the media to the host system. In addition, the control circuitry may include instruction memory (e.g., ROM, EEPROM, FLASH, and the like) used for storing firmware instructions for execution by the controller processor, and execution memory (e.g., SRAM) used for storing temporary variables, intermediate results, and the like (scratchpad).
Conventional hard disk drives and other peripheral storage devices typically perform many of the data transfer functions via a DSP or other processor executing firmware instructions. Such transfer functions include management of the buffer memory so as to facilitate transfer of data between the host and the storage medium. In this regard, the primary purpose of the buffer memory is for temporary storage of information in transit to or from the platters, and buffer management is directed toward presenting the storage medium (e.g., hard disk, CD-ROM, tape or the like) as an extension of the host's memory space. Thus, an overall goal of peripheral storage devices generally, and the management of the buffer memory therein, is to provide storage and retrieval of data in a timely fashion, so as to minimize access times from the perspective of the host system.
Toward that end, conventional peripheral mass storage devices have heretofore provided counters associated with the various components thereof to track the status and contents of the medium, the buffer memory, and the data therein. Firmware is used to manage the buffer operation and segmentation thereof, wherein the counter values are read and interpreted by firmware in order to ascertain the current status of the buffer segments. However, the various counters associated with the formatter, disk and host FIFOs, and the buffer segments are unrelated to one another. Thus, the firmware in conventional peripheral storage devices must reconcile the various counter values in order to make a determination as to whether a particular data block is within the buffer.
When the storage device receives a host command from the host computer system, either requesting a read of certain blocks of data from the medium, or asking that certain blocks be written thereto, the buffer manager firmware must scrutinize the counters to determine whether the data blocks of interest already reside in one or more buffer segments. If so, the firmware initiates the appropriate buffer component operations so as to effect the desired transfer. Otherwise, buffer segments are operated to receive the data blocks from one of the medium and the host, and to provide the blocks to the other of the medium and the host, depending upon whether a read or a write operation is to be performed. Accesses by the buffer system to the storage medium are conventionally handled with respect to sectors, tracks, zones, and cylinders, whereas host transfers are not.
Current buffer systems include separate counters for tracking storage medium and host data transfers, wherein the counter values for the disk and the counters related to host transfers are not directly comparable. In order to intelligently determine whether the data blocks needed for a particular transfer are available in the buffer, the firmware is required to read all the counter values and reconcile many different counts of how many blocks are in various buffer segments with the blocks of interest according to the host commands being processed. Thus, in present disk drives and other storage devices, the firmware has to manipulate all these values and do rudimentary additions, subtractions, and comparisons. Such low level tasks are very firmware intensive and occupy processing resources which could otherwise be utilized for higher level functions in managing the storage device. Consequently, there is a need for improved peripheral storage device apparatus and methodologies for tracking and managing buffer contents.
SUMMARY OF THE INVENTION
The following presents a simplified summary in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended neither to identify key or critical elements of the invention nor to delineate the scope of the invention. Rather, the primary purpose of this summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The invention relates to systems and methods for interfacing a storage medium, such as a disk, CD-ROM, TAPE, or the like, with a host system using a segmented buffer, and for tracking the data flow therein, by which the above mentioned and other difficulties or shortcomings associated with prior storage devices can be mitigated or overcome. The invention provides for tracking buffer contents and data transfers associated therewith according to logical block addresses (LBAs), whereby the contents of the buffer segments can be directly compared with LBAs from a host request (read or write), so as to reduce th
Brady W. James
Hudspeth David
Swayze, Jr. W. Daniel
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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