JPH0156463B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a mass storage system, and particularly to data writing in a method in which a host computer directly accesses a magnetic tape of a data cartridge without going through a magnetic disk. Regarding the time retry method.

(b) Background of the Technology A data cartridge used in a mass storage system stores a magnetic tape having a format as shown in FIG. 1 is a magnetic tape,
2 is an ID track on which a stripe number unique to each stripe is recorded in advance; 3 and 3' are servo tracks for controlling the rotary head to come to the center of the stripe; and 4 is a stripe for recording data. For example, there are 13,544 stripes, and each stripe records 4,096 bytes of data. Conventional mass storage systems have introduced the concept of virtual magnetic disks, in which the data on the magnetic tape is temporarily transferred to the magnetic disk, and the host computer accesses the magnetic disk instead of directly accessing the magnetic tape. Giving and receiving. As a typical example of magnetic tape stripes, 67 strips are combined into one.
The block corresponds to the cylinder of the magnetic disk. Therefore, the magnetic tape is divided into blocks as shown in Figure 2, with 61 data stripes, 4 for replacing defective stripes, and 2 for the system, and one stripe for the system separates each block. represent In FIG. 2, 5 indicates one block, which includes 67 stripes. 6 indicates one stripe for the system. Data is exchanged between this block and the cylinder of the magnetic disk.

When writing data to stripe 4 of magnetic tape 1, read the stripe number of ID track 2 to confirm the stripe on which data is to be recorded, then read servo track 3 to confirm the on-track, and then write data to stripe 4. At this time, if the magnetic tape 1 moves or if the magnetic tape 1 is not properly positioned by the servo signal, there is a risk that data will be written to the adjacent stripe and the adjacent stripe on which data has already been recorded will be destroyed. Therefore, if the servo track 3' cannot be read, it is determined that data writing has not been completed normally and an error has occurred that may destroy adjacent stripes. When such an error occurs, in conventional large-capacity storage systems, the data remains on the magnetic disk, so the rotary head is returned to the beginning of each block to rewrite the data, but the host computer writes the data directly without going through the magnetic disk. In the method of sending and receiving data by accessing the magnetic tape of a data cartridge, if an error occurs that could destroy an adjacent stripe while data is being written to a stripe of the magnetic tape, it is necessary to Since there is no guarantee that the data will remain in the memory of the host computer, rewriting using the conventional method as described above cannot be performed.
That is, in a system in which a host computer directly accesses a magnetic tape, it is necessary to effectively utilize the stripes of the magnetic tape and to sequentially record data sets of various lengths in order to increase processing speed. Data has various lengths, and if it is allocated to each block, unused stripes will occur, reducing the utilization rate of the magnetic tape. Therefore, in order to prevent the occurrence of unused stripes, data sets are sequentially packed and recorded as shown in FIG. In FIG. 3, 1 is a magnetic tape, and a1, a2, a3, a4, and a5 are data sets. For example, if short data such as data set a3 is allocated to one block, there will be many unused stripes and it will be wasteful, so the data will be recorded in a compressed manner as shown in the figure. In this case, if an error occurs that may destroy adjacent stripes, the data will be re-recorded. There is a problem with the trial method, and countermeasures are desired.

(c) Purpose of the Invention Based on the above requirements, the purpose of the present invention is to provide a storage means for temporarily storing data, to prevent recorded data from being erased, and to prevent an error from occurring that may destroy adjacent stripes. In this case, by rewriting the data left in the storage means, a magnetic recording and reproducing device with a high utilization rate of magnetic tape and a fast data writing processing speed in a method in which the host computer directly accesses the data cartridge can be used. The purpose is to provide a retry method.

(d) Structure of the Invention The structure of the present invention includes a plurality of storage means for storing write data, a means for reading and writing data from one of the storage means, and a method that may destroy adjacent stripes during writing of the data. The maximum amount of data to be written in one activation is the same as the maximum capacity of one of the storage means, and even if data writing to the first storage means is completed, the data will not be stored. is retained without being erased, and if an error that may destroy adjacent stripes occurs while writing data to the second storage means, the data remaining in the first storage means will cause the first The magnetic tape is rewound and rewritten so that the rotary head returns to the starting position in the data area of the magnetic tape in which the data of the storage means has been written. Also, when data is successfully written in the second storage means, the data in the first storage means is erased and new data is stored and written on the magnetic tape. If an error similar to the above occurs while writing data to the first storage means, the data of the magnetic tape on which the data of the second storage means has been written is saved. The rotary head is moved back to the beginning of the area and rewritten.

(e) Embodiment of the Invention FIG. 4 is a block diagram of a circuit showing an embodiment of the invention. Data sent from the host computer is sent to buffer memory 11 via interface 10.
When the buffer memory 11 is full of data, the data is sent to the buffer memory 12 and under the control of the control circuit 13 the multiplexer 14 sends the data in the buffer memory 11 to the write circuit 16 via the interface 15 under the control of the control circuit 17. Data is written on the magnetic tape stored in the data cartridge 19. For example, suppose that data is written in the area indicated by 21 on the magnetic tape 1 shown in FIG. The control section 13 causes the data in the buffer memory 11 to be held without erasing it, and writes the data in the buffer memory 12 in the area indicated by 22 on the magnetic tape 1 in FIG. 5 in the same manner as described above. When data writing to the buffer memory 12 is completed, the control unit 13
erases the data in the buffer memory 11 and transfers the next new data from the host computer to the buffer memory 11.
, and the data in the buffer memory 12 is held without being erased. When the error detection circuit 18 detects an error that may destroy adjacent stripes while writing data in the buffer memory 11 to the area shown in FIG. ,
The control circuit 13 instructs the magnetic tape 1 to be rewound to the beginning of the area 22 as indicated by the arrow in FIG. Assuming that the buffer memory 11 or 12 has a capacity for n stripes, it is possible to rewind the magnetic tape 1 by counting the number of stripes written until an error occurs. The control circuit 13 sends the data remaining in the buffer memory 12 without erasing it again to the write circuit 16 via the multiplexer 14 and the interface 15 to area 2 of the magnetic tape 1 in FIG.
Rewriting is performed from the beginning of 2.

Although this embodiment has been described using hardware, it goes without saying that the above operations can be performed using software using the storage area of the host computer.

Also, although the number of buffers has been explained as two, three or more will have the same or greater effect.

(f) Effects of the Invention As explained above, the present invention can be used in a mass storage system in which a host computer directly accesses a magnetic tape, even if an error occurs during data writing that may destroy adjacent stripes. The effect is great because it provides a way to retry without any problems.

[Brief explanation of drawings]

Figure 1 is a diagram showing the format of magnetic tape.
FIG. 2 is a diagram for explaining blocks of a magnetic tape, FIG. 3 is a diagram for explaining an example of recording a data set on a magnetic tape, FIG. 4 is a block diagram of a circuit showing an embodiment of the present invention, and FIG. The figure is a diagram explaining the data recording method of the present invention. 1 is a magnetic tape, 2 is an ID track, 3 and 3' are servo tracks, 4 is a stripe, 5 is a block, 10 and 15 are interfaces, 11 and 12 are buffer memories, 13 and 17 are control circuits, 14 is a multiplexer, 16 is a write circuit, 18 is an error detection circuit, and 19 is a data cartridge.

Claims (1)

[Claims] 1. In a magnetic recording and reproducing device that uses a rotating head to record or reproduce data on stripes formed perpendicularly or diagonally to the longitudinal direction of a recording medium, a plurality of storage means for storing written data and a plurality of storage means for storing written data are used. Means for reading and writing data from one stripe and means for detecting the occurrence of an error that may destroy adjacent stripes during writing of the data are provided, and the amount of data written in one activation is determined by the storage means. The maximum capacity of one of the storage means is set to one of the maximum capacities, and the data is retained without being erased even after data writing to the first storage means is completed, and an error that may destroy adjacent stripes is prevented during data writing to the second storage means. 1. A retry method for a magnetic recording/reproducing apparatus, characterized in that, if this occurs, rewriting is performed from a data recording area of the first storage means using the data of the first storage means.