Electrical computers and digital processing systems: memory – Storage accessing and control – Memory configuring
Reexamination Certificate
1998-07-01
2001-09-11
Yoo, Do Hyun (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Memory configuring
C711S004000, C700S214000
Reexamination Certificate
active
06289425
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a virtual tape data storage arrangement, and more particularly to an improved method for verifying whether data space on a scratch tape is reusable which increases efficiency by minimizing the movement of data.
BACKGROUND ART
Generally, automated cartridge systems (ACS) provide a mechanism by which multiple users in a data processing system can have common access to multiple data storage subsystems such as magnetic tape cartridge devices. In conventional tape systems, data files generated by remote user computer systems for storage on a particular tape cartridge include a predetermined expiration date which is used as a control mechanism by which a tape management subsystem can determine whether a particular space on a tape can be rewritten with new data. However, in conventional tape systems, expired data from a “scratched” tape volume is not actually deleted from the tape until a user actually writes new data to the tape, thereby significantly decreasing the efficiency in reutilizing data storage space.
In response, a virtual tape system has been developed which significantly improves storage space utilization and control by incorporating the advantages of an intermediate disk buffer as part of a tape emulation arrangement. Such an arrangement is taught in commonly owned copending U.S. patent application Ser. No. 09/110,217 (attorney docket number 97046TAP/STK97046PUS), filed on Jul. 6, 1998 , and incorporated herein by reference.
More specifically, in the referenced virtual tape system, a disk buffer is connected between remote users and the tape storage devices and arranged to appear to users as though it were a physical tape device. All data volumes are initially stored in the disk buffer, and subsequently written to a physical tape device using predetermined protocols which limit the occurrence of unusable dead spaces on the tapes while also improving the ability to reclaim any fragmented space which does occur.
However, before a particular tape volume can actually be reused, a tape management subsystem will request mounting of a scratch tape to a tape drive, i.e., a scratch tape is a tape which no longer contains any unexpired data, and examine all volume label and header label information stored on the tape to verify whether the corresponding data stored on the tape has expired and can be overwritten by the system.
The problem with such an arrangement derives from the fact that to analyze the volume and header information, the entire virtual volume must be recalled into the disk buffer from the tape to make the label information available to the tape management subsystem. This in turn produces substantial processing delays and a decrease in overall system efficiency due to the required movement of data simply to verify that the data can be overwritten if expired.
One known arrangement has attempted to overcome this problem by creating a duplicate file of volume labels and headers when the volumes are originally stored on a tape, and maintaining the duplicate volume labels and headers in a resident memory in the interim buffer of the virtual tape system. However, such an arrangement is not fully satisfactory because of the substantial added cost and complexity of constantly maintaining all label information in the resident memory. As a result, a need exists for an improved method of verifying the availability of reusable data space on a scratch tape in a virtual tape system which minimizes both data movement and additional cost and complexity to the virtual tape system.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide an improved method for verifying availability of reusable data space on a scratch tape in a virtual tape system which improves data space reutilization efficiency.
It is another object of the present invention to provide a method for verifying availability of reusable data space on a scratch tape in a virtual tape system which minimizes the need for data movement between the tape and a disk buffer.
It is a further object of the present invention to provide a method for verifying availability of reusable data space on a scratch virtual volume in a virtual tape system which does not require physical mounting of a tape to a physical tape drive mechanism.
In accordance with these and other objects, the present invention provides a method for verifying availability of reusable data space on a selected scratch tape in a virtual tape system which utilizes volume label information routinely maintained in an external tape inventory management arrangement to generate a separate file of labels in a compatible format for input to a tape management subsystem in communication with the virtual tape system after the selected virtual tape has been retrieved from an interim buffer in the virtual tape system, i.e., “mounted” on a virtual tape drive.
In accordance with one aspect of the present invention, the method comprises receiving a request for mounting a scratch tape, selecting a scratch tape for mounting on the virtual drive, and generating a tape volume label comprising information of a corresponding virtual volume stored on the selected scratch tape. The generated tape volume label is generated in a format compatible for use by an external tape management system based on preexisting file meta data maintained external to the virtual tape system and the selected tape. The generated tape volume label is then input into the external tape management system for determining whether any unexpired data is stored on the selected tape. The scratch tape is reused for storing new virtual volumes if there is no unexpired data on the virtual tape. Otherwise, the generated tape volume label is destroyed and the file meta data for the virtual volume is updated to indicate that unexpired data is present on the selected tape. The preexisting information maintained external to the virtual tape control system is originally derived from actual meta data information included with volume files stored on the tape.
With such an arrangement, the present invention can allow a tape management system in the virtual tape system to verify whether a selected scratch tape contains only expired data which can be written over without copying the entire virtual volume data from the physical tape into a disk buffer, and without requiring physical mounting of an actual tape to a physical tape drive. This significantly reduces processing time and needless data transfers, thereby increasing overall efficiency in data storage management and storage space utilization.
These and other objects, features, and advantages of the present invention will be readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.
REFERENCES:
patent: 4467421 (1984-08-01), White
patent: 5455926 (1995-10-01), Keele et al.
patent: 5805864 (1998-09-01), Carlson et al.
Blendermann Stephen H.
Sutton Alan Ray
Brooks & Kushman P.C.
Moazzami Nasser
Storage Technology Corporation
Yoo Do Hyun
LandOfFree
Method for verifying availability of data space in virtual... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for verifying availability of data space in virtual..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for verifying availability of data space in virtual... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2459736