Dynamic magnetic information storage or retrieval – Head – Coil
Reexamination Certificate
1998-02-05
2001-02-27
Heinz, A. J. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Coil
C360S125330
Reexamination Certificate
active
06195231
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and system for storval of a plurality of binary information (data) involving a plurality of data transfer transducer means (simultaneous data transfer head means) and a data disk storval means. This simultaneous data storval means can be used in computer systems and other data processing systems utilizing data storval on rotatably mounted disk storval means and the disk means themselves. As generally defined, a storval means is a means for storing, retrieving, or erasing data on or in a device. Specifically, this invention is used with rotatably mounted disk storval means.
BACKGROUND OF THE INVENTION
Computers have a need for the storage of binary information on different types of mediums for eventual retrieval for processing in their central processing unit (CPU). This has led to different types and speeds of storval devices, from temporary to long term storval requirements. The speed of access to the information for the various types varies widely. The major classifications of storval devices associated with computer systems are: (1) immediate-access (typically core and cache storage); (2) random access (typically RAM or other devices in which the time to obtain information is independent of the location of the information most recently obtained); and (3) sequential access (typically storval devices in which the items or information stored become available only in a one-after-the-other sequence, whether or not all the information or only some of it is desired. (Typically disk, tape or drum storage). Information can be stored as either program instructions for the computer to execute in the CPU or as data used for computations. In this patent, data will refer to both program instructions and data interchangeably.
A random access memory (RAM) is a solid state type of device manufactured from semiconductor materials that retains information only as long as the machine is running. It has the advantage of nearly instant access for the CPU (from 10 nanoseconds to 150 nanoseconds) when the data is called for. However, this type of storval has been typically very expensive in the past. For intermediate long term storage, a hard disk with a magnetic coating on its' surface can presently store data without loss for as long as ten years, with access times of 4 milliseconds to 30 milliseconds. Intermediate storval of data is data that might be required by the CPU in its daily operations on an occasional usage. For long term storage, that is, storage that requires the archiving of information, a photo-optic storval disk that uses lasers for reading the information, called a CD Rom, should store data for 100 years or more, with present access times of typically more than 200 milliseconds.
For intermediate storval of data, it has been a long sought goal to use an inexpensive system while providing a computer with faster access to data and, also, to increase the capacity for storval of data. The time for a data storval operation using a disk utilizing a sequential data transfer head means is comprised of seek, latency and command overhead times. Referring to
FIG. 1
, seek time is defined as the time required to position a sequential data transfer head means
180
-
1
above a particular track
174
. The shorter distance the sequential data transfer head means
180
-
1
has to travel, the shorter the seek time. Referring to
FIG. 3
, latency time is defined as the time required for the disk
372
to rotate beneath a positioned sequential data transfer head means
380
-
1
until a predetermined sector of the track
374
rotates past the sequential data transfer head means
380
-
1
. The faster the disk rotates, the smaller is the latency time.
Data storval disk controllers, the “brains” that control the devices, can pre-access the data before it is required by the CPU and store it temporarily in a data cache. The data cache is typically a RAM device that can store relatively small amounts of data. When the data needed by the computer is stored in cache, both seek and latency times are eliminated. Caching includes CPU cache, RAM cache, hard drive cache, track buffering, pre-fetching and write cache. CPU cache stores a part of a program or data so it may be accessed quickly while the CPU is executing the program. RAM cache is used for storing the most frequently accessed disk information and speeds data retrieval but limits the amount of RAM available for the program itself. RAM cache minimizes small computer system interface (SCSI) bus traffic by serving I/O requests within the computer itself. Hard drive cache is located on the controller board and is slower than RAM cache. Hard drive cache stores the most recently requested disk information and frees the computer RAM for running the program. Track buffering works on the principle that when data is requested from a particular sector, it is likely that the CPU will then require data located in adjacent sectors. In anticipation, the controller reads the entire track and stores the read data in its RAM. This speeds up information retrieval for most applications. Pre-fetching is similar to buffering except it reads the next track by a sequential data transfer head means before it is required.
Command overhead time is the time required for the computer command to be interpreted and acted upon by the data storval controller. While this is taking place, requested data stored in the called for sectors of a track may have passed beneath the sequential data transfer head means requiring the rotation of the disk means almost a full revolution before the called for sector is once again located beneath the sequential data transfer head means. Interleaving and sector skewing are used to reduce this amount of command overhead time.
The central processing unit (CPU) of some computers cannot handle data as quickly as the hard drive controller can transfer data on the spinning disk. By the time the CPU digests the information that the sequential data transfer head means has just transferred data from one sector and issue orders to the disk controller to perform another data storval operation, the predetermined sector on the spinning disk may have already passed by the sequential data transfer head means. To perform the storval of data the disk device controller controlling the sequential data transfer head means must wait a full disk rotation for that sector to once again pass beneath the sequential data transfer head means. A disk controller is a circuit that transmits and retrieves signals to the disk drive. In a personal computer a disk device controller is a printed circuit board that plugs in the expansion spot in the bus or is a printed circuit board that contains circuits that reside in or near the disk housing.
Interleaving describes how sectors are arranged on the disk, so that the device controller controlling the sequential data transfer head means can transfer data in the fastest possible sequential order. This is illustrated in FIG.
12
. The information allotted to ordered sectors does not follow the sectors actual sequential numerical order; information is placed on sectors that are not physically contiguous, as can be seen from the arrows in FIG.
12
. As shown in this figure, the data storval occurs first from sector
1
, then from sector
10
, then sector
20
, then sector
30
. Thus the device controller controlling the sequential data transfer head means doesn't have to wait a full rotation for the sector the sequential data transfer head means has missed to come by again.
Sector skew optimizes transferring information on adjacent tracks, in much the same way interleaving optimizes movement within a track. It does this by taking into account the time it takes the sequential data transfer head means to move to another track and the distance a sector will travel in that time (due to the disk's rotational speed), and then offsetting the numbering for the sectors on the next track.
The time for storval of a particular piece of data on a rotatably mounted disk means would
Burton Duane
Sedlmayr Steven R.
Burton Duane
Heinz A. J.
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