Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1999-04-09
2001-09-25
Nguyen, Than (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S111000, C711S112000, C711S113000, C711S147000, C711S154000, C711S155000, C709S211000, C709S212000, C709S213000, C710S110000
Reexamination Certificate
active
06295578
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to secondary or back-up data storage systems for individual computers or computer networks; more particularly, the present invention pertains to an improved data system for secondary or back-up storage of data on removable media such as tape cartridges.
BACKGROUND OF THE INVENTION
Computer Data Storage
Computer data storage which is co-located with a host, server, or an individual computer is placed in a section of computer memory designated primary storage. This primary storage provides the computer with the capability to process program instructions, to store input data, to retain statements from programs undergoing processing, to retain and use data produced by programs undergoing processing, and to format data in preparation for output.
Initially data which goes into the computer is held in primary storage until the data is used during the processing of program instructions. During processing of the data by the computer, the primary storage is used to store the intermediate and final results of all arithmetic and logical operations. Intermediate results are temporarily retained in storage areas which are often referred to as working storage. Working storage areas are specifically set aside for the temporary storage of data while a program is being run on one or more computers. While the computer is running the program and using the data, the computer may be acting as if all program instructions and needed data are resident in its main memory; however, the program instructions and data may actually be located miles away at another location and downloaded into the computer as if resident in the computer's primary storage. Such storage configuration is called virtual storage. The final results from the running of a computer program are transferred to storage areas that have been designated by the program instructions. These final results will remain at the designated storage areas until output operations begin.
In addition to storing the data involved in processing, the primary storage of a computer must retain the program instructions used for processing data. As computer applications have become more sophisticated, the size of computer programs has grown exponentially. Such exponential growth in the size of computer programs has necessitated the use of virtual storage of computer programs or data in locations away from the host or server computer to enable sufficient space in primary storage to run other large computer programs.
For example, a large international bank may have a designated time each day to consolidate all of the transactions from its branches around the world. Once this daily consolidation has taken place, the massive amount of consolidated data must be stored somewhere for later use in putting together periodic account statements and to provide the specialized reports necessary to meet regulatory and tax requirements. Such specialized reports could not be run unless the bank's computer had access to large virtual data storage capacity.
Secondary or Back-up Data Storage
Because of the ever growing need for data storage capacity to service larger and larger computers which run larger and larger programs—all of which produce massive amounts of data—the need has arisen for larger and more sophisticated secondary or back-up data storage systems. Secondary data storage provides a computer system with greater data processing potential because it expands the amount of available storage space to a computer or a computer network for holding data. The data contained in secondary or back-up data storage may be too large to be held in primary or working storage; however, to allow the program resident in the host or server computer network to run, data storage space must be located and made available to the host or server computer as quickly as possible for data writing and data reading operations. By providing a host or server computer network with large amounts of secondary or back-up data storage capacity, the operational capabilities of individual computers or a computer network can be maximized.
Removable Media
One of the most used forms of secondary or back-up data storage device hardware is a removable media data storage unit. While slower and possibly more cumbersome than other types of secondary data storage, removable media data storage units such as tape cartridges remain a viable and frequently used data storage option because of its low cost and acceptance around the world.
Because of the way data is actually placed on one or more individual removable media data storage units, a removable media data storage system includes a controller to govern its operation. The removable media data storage system controller is used to divide computer programs and associated data into sections to guide the data being written onto one or more removable media data storage units from the host or server computer network to an individual removable media data storage unit. Such guidance from the removable media data storage system controller as to the path by which data is written on one or more individual removable media data storage units should be invisible to the host or server network. Rather, all the host or server computer network needs to retain is a “volume number” designating the location of the stored data. The term “volume number” actually comes from early magnetic tape data storage systems where a volume number was the identification number of a single reel of magnetic tape. Presently, a “volume number” may identify a single removable media data storage unit or a group of removable media data storage units where data is written to or read from.
When stored data is to be read back to one or more computers in a network of host or server computers, the removable media data storage system controller retrieves the stored data from the one or more removable media data storage units where it is actually stored and supplies the stored data to the host or server computer as if the data came from a single volume number location.
Data Storage on Multiple Removable Media Units
Because one of the problems in reading and writing data onto individual removable media data storage units is the lack of speed in the sequential access of data, the speed of either writing to or reading from secondary or back-up data storage on a removable media data storage unit has been greatly increased by the use of mass removable media data storage systems such as mass tape cartridge data storage systems which employ strips of magnetic tape in an ordered array. In these mass tape cartridge data storage systems, any data recorded in a tape cartridge can be accessed directly without having to search the entire contents of the tape cartridge.
In many removable media data storage systems, data is stored by a process known as striping. In striping a serial or linear sequence of groups or bytes of data is downloaded by parallel data groups into parallel groups of individual removable media data storage units. (In early magnetic tape data storage systems, bytes of data were written sequentially in a serial manner onto a single roll of magnetic tape. The single roll of magnetic tape then had to be either wound or unwound to gain access to the correct length of magnetic tape holding the needed data to read the needed data back into the computer.) Thus, if seven individual removable media data storage units are available for data storage, data can be written to storage on the removable media data storage unit or read from storage on the removable media data storage unit in groups of seven stripes.
Access to groups of individual removable media data storage units is typically accomplished by the use of robotic control or a robot. The removable media data storage system controller directs the robot to the group of individual removable media data storage units on which data is written to or read from. The robot then locates the appropriate group of individual removable media data storage units designated by the removable media data storage system
Dimitroff John E.
Grant David L.
Compaq Computer Corporation
Fletcher Yoder & Van Someren
Nguyen Than
LandOfFree
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