JPH0469880A - Magnetic tape storage device - Google Patents

Abstract

PURPOSE:To shorten the access time to a file data by accessing a dedicated memory stored with information for managing the file data recorded on a magnetic tape when a tape cartridge is set in the device. CONSTITUTION:The dedicated memory 11 for making the file management information always resident is provided in the magnetic tape storage device. When the tape cartridge is set in the device, the file management information recorded in a leading part of the tape is read and stored to always reside in the memory 114 before an instruction for requested to be read out, the tape is moved to an area recorded with the file data by referring to the file management information stored to always reside in the memory 114, and hence the data is read out.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention utilizes a digital VTR, DAT (digital audio tape recorder), etc. as an external storage device for a computer to digitally record data onto a magnetic tape. The present invention relates to a magnetic tape storage device for recording.

[Conventional technology]

Hard disk drives have become popular as auxiliary storage devices for personal computers (PCs). but,
Hard disks have a limited data storage capacity because the media cannot be replaced and cannot be riffled, and there is a risk of data loss due to media damage, so it is necessary to periodically back up the data. However, currently the most popular hard disk device has a storage capacity of 20 megabytes.
Alternatively, it has a large capacity such as 40 megabytes, and it is thought that hard disk drives with even larger capacities will become widespread in the future. When backing up using a floppy disk with a capacity of 1 megabyte, the number of media required for backup is 10 to 40, making it impossible to back up easily. Therefore, there is a growing need for a storage device with a large storage capacity that is compact and replaceable, and the development of a magnetic tape storage device that applies digital V'l''I and DAT is progressing.l) A
In the case of T, audio signals are originally used for music or other purposes on a PC.
By converting to M, it is converted to a digital signal and recorded on magnetic tape using a rotating head. When this DAT is applied to data storage, a 120-minute music tape has a capacity of approximately 1.4 gigabytes. Becomes a large capacity storage device. Furthermore, it can be used as a large-capacity filing system by using AT's unique high-speed search function to randomly access tapes and make partial corrections and additions to data. It is being considered. However, 1) Magnetic tape storage devices that apply AT are inferior in terms of access speed when compared to disk devices such as hard disk devices and floppy disk devices.
Therefore, for example, as in Japanese Patent Laid-Open No. 1-73561, it has been proposed to efficiently output data by providing a buffer memory for data inside the magnetic tape storage device.

[Problem to be solved by the invention]

When using a magnetic tape storage device as a peripheral device for a personal computer, it is desirable to use the same control means as a disk device, considering the file operations on the floppy disk device or hard disk device installed as an auxiliary storage device in the computer. It will be done. - Generally, peripheral devices of a personal computer are controlled by software called an operating system, and an area for recording file management information is provided at the beginning of the medium. Therefore, when reading file data, the file management information present at the beginning of the medium must be read before accessing the file data recording area. When writing file data, the file data must be read. After writing, move the head to the beginning of the media and modify or add file management information. When such a file access method is used in a magnetic tape device, the tape moves frequently and the distance the tape moves becomes long, resulting in a slow file access speed. Furthermore, frequent access to the same area causes the tape to deteriorate, leading to loss of file data.

[Means to solve problems]

A dedicated memory for storing file management information is provided inside the magnetic tape storage device. When a tape cartridge is set in the device, the file management information recorded at the beginning of the tape is read and made to reside in the dedicated memory described above until a tape ejection request command is issued.

[Effect]

When a tape cartridge is set in a magnetic tape storage device, file management information is read from the beginning of the tape and stored in a dedicated memory provided inside the device.

Access requests to the tape can be accepted after the file management information is resident in the dedicated memory. When there is a request to read file data, the tape is moved to the area where the file data is recorded by referring to the file management information resident in the dedicated memory, and the data is read. When there is a request to write file data, the system refers to file management information stored in the dedicated memory, searches for an area where file data can be recorded, moves the tape, and writes file data.

If a file name that matches the file name of the written file data exists in the file management information, the contents of the data stored in the dedicated memory are rewritten, and if it does not exist, it is added to the file management information in the dedicated memory. do. By providing these functions, the number of accesses to the file management information area recorded on the tape can be reduced, and the time required for file access can be shortened.

〔Example〕

As an embodiment of the present invention, a case will be described in which a DAT system (hereinafter referred to as a DAT recorder) developed as an external storage device for a computer by applying DAT is used. A block diagram of the system used in this example is shown in FIG. A cylinder 101 to which a rotating head is attached, a cylinder motor 102 that rotates this cylinder, a capstan motor 103 that runs the tape at a constant rate, a reel motor 104 that performs fast forwarding and rewinding, a servo circuit 105 that controls these motors, and a rotating head. A read/write circuit 106 that writes and reads signals using the DAT, a DAT signal processing circuit 107 and a subcode control circuit 108 that process signals according to the DAT format, instructs the mode of the device, and instructs the drive of the mechanism. A drive control circuit 109 that receives this signal and drives the mechanism, a loading motor 111 that is controlled by the mechanical drive circuit and used for loading the tape, and an error correction code according to the DAT format. DAT encoding/decoding circuit 112 and layered FCC circuit 113 for encoding and decoding, memory 114 for storing data and layered FCC encoding/decoding, and controlling reading and storing of data from this memory. A memory control circuit 115, a system control circuit 116 that controls all of these, and an interface control circuit 117 that connects with the host computer.
, dedicated memory 11 for storing file management information
8. Detection circuit 119 for detecting tape cartridges
, a host 5C5I (small computer system interface) adapter circuit 120, and a host computer 121.

Next, the basic operation of the DAT recorder will be explained.

“Loading Operation” When it is detected that a tape cartridge is set in the device, the system control circuit 116 performs a loading operation.
The motor 111 is driven to pull out the tape from the tape cartridge and wind it around the cylinder 101. When the tape is loaded, system control circuit 116 sends a signal to drive control circuit 109 to perform rewind, and drive control circuit 109 sets servo circuit 105 to rewind mode. The servo circuit 105 connects the reel motor 10
4 to perform rewinding, and rewinding of the tape is started. When the tape is rewound and the drive control circuit 109 detects a transparent part of the tape, the servo circuit 105 is set to the stop mode, and the system control circuit 11
6 to notify that tape rewinding has been completed.

“Read operation” When there is a data read request from the host computer 121, the drive control circuit 109
5 into the play mode, and the signal processing circuit 107 into the read mode. The servo circuit 105 controls the reel motor 104 and rotates the magnetic tape at 8 mm/15 mm/mm as specified by the standard.
The servo circuit 105 captures and controls the rotational speed of the cylinder lot so that the cylinder lot is driven at a constant speed of s and the cylinder 101 is rotated at a constant speed of 200 rpm. 18 in this cylinder 101
1, in which the ATF recorded on the tape is read by two rotary heads mounted facing each other at 0 degrees, and the signal processing circuit 107 inputs a servo signal to the servo circuit 105 via the read/write circuit 106; The servo circuit 105 controls the rotation speed of the cylinder 10 and performs 1. Allows you to trace your tracks correctly. A No. 11 processing circuit 107
receives this signal and outputs it to the subcode control circuit 108 as a signal in the subcode area. Receive this signal
] The subcode control circuit 1.08 converts the subcode from this signal. It reproduces the data, detects a parity error, and sends the result to the drive control circuit 109. The data read by both heads is processed by the belief processing circuit 107 (III).
) A T code-/decoding circuit 1] is transferred to the DAT
It performs error detection and correction according to the format, and requests data transfer to the memory control circuit 115.

The memory control circuit 115 transfers this data to the layered FCC circuit [3], performs error correction according to the error correction algorithm, and then transfers the data to the layered FCC circuit [1].
41\Storage. The system control circuit 116 controls the memory 1
The decrypted data stored in the computer 14 is transferred to the host computer 121 via the interface control circuit.

"F write operation" When there is a data write request from the post computer 121-, the system control circuit]]6 sends the data to Also provides instructions for transfer. The memory control circuit 11E) that receives the data transfer request via the interface control circuit receives the data and stores it in the memory 114. The system control circuit 11 () is a memory control circuit 111), and the eared Ipecc circuit 113
The data is then encoded according to the layered ECC format. This data is transferred to the encoding/decoding circuit] 12, where it is encoded based on the DAT standard, and then transferred to the ID code processing circuit 107. The signal processing circuit 107 receives subcode data from the subcode control circuit 108, switches the mode to write mode, and records it on the magnetic tape via the read/write circuit 106.

[Search operation J] If you run the tape at high speed while it is wrapped around the cylinder] and control the relative speed between the tape and the rotating head to be the same as during normal loading/writing, the recorded data can be retrieved. 1. In order to perform the search at double speed, the tape running speed should be 100 times the normal cylinder 10]? must be rotated.

Therefore, the rotational speed of the cylinder 101 is 3000 rprn in the case of forward search, and OOOr p rrl in case of reverse search. Since the number of tracks the head crosses is determined to be 1.00 and 400, the reel motor 1.04 is controlled so that the number of tracks the head crosses becomes a predetermined number.

The data read out intermittently in this way is taken out by the signal processing circuit 107, and the data is inspected by the subcode control circuit 108 and the drive control circuit 109. By reading the subcode data and PCM-ID contents,
You can search for the desired area.

Next, the operating system used in this example will be explained. FIG. 2 shows the tape format of the operating system used in this embodiment. A spare area for loading is provided at the beginning of the tape,
At the location following the spare area, there is a FAT (File Allocation Table) that points to the storage area for file data, and 1 to prevent data loss due to destruction of the FAT area. Created when copying AT data or formatting a tape. Furthermore, in the position following the copy of FA T and knee"AT, file name 4 file creation month and date.

A directory area is secured for recording file capacity, FAT location corresponding to the file, and the like.

Therefore, file data is recorded starting from the end of the directory area. Human output of data is performed in units of fixed length called sectors, and the sector size multiplied by 2 is used as a unit for file management and is called a cluster. The sector size and cluster size can be selected within hardware limitations.

A sector number is assigned for each sector size from the beginning of the tape, and a cluster number is also assigned for each cluster size. A data input/output request from an operating system to a storage device is made based on the sector number and number of sectors from which reading or writing is to be started. FAT corresponds to cluster numbers, and the cluster number in which a file is recorded can be found.

When a file read request is received from a computer user, the specified file name is searched by referring to directory information and the FAT location is obtained. By reading the FAT information, the cluster number in which the specified file data is recorded is obtained. The obtained cluster number is converted into a sector number, and the tape is moved to the first sector where file data is recorded to read the data. When writing, the directory area is referenced to check whether the specified file name already exists, and the handling is different depending on whether it exists in the directory information or not. If the file already exists in the directory information, read the FAT data according to the FAT position information recorded in the directory area, move the head to the cluster pointed to by FAT, and read from above the already existing file data. Override. If the size of the new file data to be written is larger than the size of the existing file data and does not fit into the cluster that was already in control, refer to the FAT data and search for a cluster to which no data has been written. However, it records file data. When writing data to a new disk, after writing the file data, the head is moved to the FAT area again and the FAT data is rewritten. If the file data specified for writing does not exist in the directory information, FAT
Browse the data and search for clusters where no file data has been written. After writing the file data,
Move the head to the FA and T areas and rewrite the FAT data. If the file data spans multiple clusters, this operation is repeated until all the file data has been recorded. When the recording of file data is completed, it moves to the directory area and records directory information such as the file name and creation date.

The above is the file management method by the operating system used in this embodiment.

The DAT recorder used in this example uses a 60m tape (
Approximately 1 gigabyte of data can be stored on a 120-minute music tape, but due to operating system limitations, only 64 megabytes or less of storage capacity can be controlled. Therefore, as shown in FIG. 3, the tape is divided into 64 megabyte areas (partitions) and files are managed for each partition. Once a partition is specified for input/output, the tape is moved to the beginning of the partition, and access to other partitions is not possible until the next partition is specified. Inside a partition, local sector numbers are assigned from the beginning of the partition. Therefore, each partition can be considered an independent medium, and each partition needs to have a directory area and a FAT area. but,
Since it is not desirable for file management information to be dispersed within the tape, this information is recorded all at once at the beginning of the tape.

Flowcharts of this embodiment are shown in FIGS. 4 to 7. Figure 4 shows the operation when the tape cartridge is set in the device, Figure 5 shows the read/write operation, Figure 6 shows the tape cartridge eject operation, and Figure 7 shows the operation when the external power supply is cut off. This is a flowchart. As shown in FIG. 4, when a tape cartridge is set in the device and detected by the detection circuit, the tape is loaded and the FAT information and directory information of each partition recorded at the beginning of the tape are read out. The read data is transferred to and stored in a dedicated memory 118 newly provided inside the device. However, the first byte of the dedicated memory 118 is an information area for determining whether the contents stored in the memory 114 have been changed, and is set to O in the initial state. The file management information is written from the second part of the dedicated memory 118. In this embodiment, the sector size is set to 024 bytes, the cluster size is set to 4 sectors (4 kilobytes), the FAT area of each partition is set to 4 kilobytes, and the directory area is set to 4 kilobytes. Therefore, dedicated memory】1
The file management information stored in 8 is (8 kilobytes) x (number of partitions). The operating system recognizes each partition as an independent medium, and recognizes the I'AT area and directory area as existing at the beginning of the partition3. Instructions from the operating system are , is specified by the media number, sector number, and number of sectors (data length) to be output.

l) When the AT recorder receives a file data input/output command from the operating system, it moves the tape to the beginning position of the partition corresponding to the specified media number and checks the sector number specified for human output. do. If the head is already positioned at the specified partition, the tape is not moved to the beginning of the partition again, but the sector number is checked. If the specified sector number is 8 or higher, it is an access request to the FAT area or directory area, so the data stored in the dedicated memory 118 is accessed without accessing the magnetic tape. . When rewriting data recorded in the dedicated memory 118, the byte information provided at the beginning of the dedicated memory 118 is set to 1. If it is any other sector number, this is a file data input/output command, and the magnetic tape is accessed via the data buffer. When there is a request to take out a magnetic tape from the host computer 121, as shown in FIG.
Referring to the first byte of No. 18, only when the byte data is 1, the magnetic tape is rewound and the FAT and directory information stored in the dedicated memory 118 are recorded on the magnetic tape. After confirming that the file management information has been recorded on the magnetic tape, the magnetic tape is rewound until the leading transparent portion is detected, and the tape cartridge is ejected. If the first byte data of the dedicated memory 118 is O, the information recorded in the dedicated memory 1], 8 is not recorded on the magnetic tape, the magnetic tape is rewound to the beginning, and the tape cartridge is ejected. do. Originally, the first byte data of the dedicated memory 118 is O or 1, but if it indicates any other value, the data of the dedicated memory 118 is recorded in a spare area provided after the file data area of the magnetic tape. , host computer], 2
1, a message is sent to inform that the file management data is abnormal, the magnetic tape is rewound to the beginning, and the tape cartridge is ejected. This device is
It operates using power supplied from the outside, but if the power supplied from the outside is cut off, the power source is switched to a storage type power supply provided inside the device. In such an emergency case,
The operation shown in FIG. 7 is performed. If there is unrecorded data on the magnetic tape in the buffer, recording is performed on the magnetic tape l\, and the magnetic tape is rewound to the beginning of the tape. After positioning the tape to the FAT and directory information recording area of each partition provided at the beginning of the tape, the FA stored in the dedicated memory 118 is
Record T data and directory data on magnetic tape. After confirming that the file management information has been recorded,
The magnetic tape is rewound until a transparent portion is detected, and the tape cartridge is ejected.

〔Effect of the invention〕

According to the present invention, when a tape cartridge is set in a device, information for managing file data recorded on a magnetic tape is stored in a dedicated memory provided inside the device, and access to a file management information area is made possible. Data stored in dedicated memory is accessed without accessing the magnetic tape in response to requests, so there is no need to move the tape to the file management information area in response to requests to read, output, or write file data. Therefore, the time required to access file data can be shortened.

Furthermore, since the number of accesses to the file management information area recorded on the magnetic tape is reduced, it is possible to prevent deterioration of the medium and improve the reliability of file data.

Even when file management is performed by dividing a magnetic tape into multiple areas (partitions), by recording the file management information for each partition at the beginning of the magnetic tape, when a tape cartridge is set, Regarding storage of file management information in the dedicated memory, there is no need to move the magnetic tape to each partition, and the time required to read the file management information can be shortened.

If the power supply is cut off while the device is in operation,
Power is supplied by a storage type power supply installed inside the device, and the file management information stored in the memory is recorded on magnetic tape, so the file management information rewritten in the memory is not lost and the file The reliability of management information is maintained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a tape format diagram of the operating system used in this embodiment, Fig. 3 is a tape format diagram of this embodiment, and Fig. 4 is a diagram of the tape format of the operating system used in this embodiment. A flowchart of the operation when a tape cartridge is set in the device, Figure 5 is a flowchart of the read/write operation, Figure 6 is a flowchart of the ejection operation of the tape cartridge, and Figure 7 is a flowchart of the tape cartridge being supplied from the outside. It is a flowchart of the operation when the power is cut off. 101... Cylinder, 1.02... Cylinder motor, 103... Capstan motor, 104... Reel motor, 105... Servo circuit, 106... Read/Write circuit, 107... Signal processing circuit, 108... Subcode control circuit, 109... Drive control circuit, 110... Mechanical drive circuit, 111... Loading motor, 112... Encoding/decoding circuit, 113... Layered FCC circuit, 114...Memory, 115...Memory control circuit, 6...System control circuit, 7...Interface control circuit, 8...File information dedicated memory, 9...Detection circuit, 0...Host 5C3I adapter circuit, 1...Host computer.

Claims (1)

[Claims] 1. In a storage device that records and reproduces file data on a magnetic tape, a detection circuit for detecting attachment/detachment of the magnetic tape is provided, and the file recorded on the magnetic tape set in the device is detected. A magnetic tape storage device comprising a dedicated memory for reading and storing file management information such as an identifying file name and information indicating an area in which the file data is recorded from the magnetic tape. 2. In claim 1, a detection circuit detects that a tape cartridge is set in the device, reads the file management information into the dedicated memory and makes it resident, and in response to a tape ejection request, the resident data is A function to write resident data to tape only when it has been changed, and a function to read the file data by referring to the file management information resident in the dedicated memory in response to a read request for the file data. and a function of recording the file data on a tape and modifying or adding the file management information resident in the dedicated memory in response to the file data write request. 3. In claim 2, the magnetic tape has a function of dividing a magnetic tape on which data is recorded into a plurality of areas for file management, and sequentially recording the file management information of each area at the beginning of the tape. Tape storage device. 4. According to claim 2, the device comprises a storage type power supply for supplying power inside the device, and when the power supply from outside the device is cut off, the magnetic tape is rewound and the file management stored in the memory is provided. A magnetic tape storage device having a function of recording information at the beginning of the magnetic tape.