JPS595407A - Storage device having plural heads - Google Patents

Abstract

PURPOSE:To shorten remarkably a data change processing time, by providing two heads, updating a read data by the preceding head, and writing a changed data by the following head. CONSTITUTION:The first head 4 and the second head 5 are fitted in the rotating direction of a disk 1. When the head 4 reaches the head position of a record Rn, a read operation is started by a read circuit 7, and a data of the record Rn is transferred to a data storage part 10. Subsequently, when the head 4 moves by length l1 of the record Rn and becomes a state 2, the read operation is stopped. Subsequently, while the head 5 moves by length l2 of a track 2, a data controll circuit 13 changes a data of the record Rn of the storage part in accordance with a request of a processing device of a host. When it is confirmed by a record position confirming circuit 11 that the head 5 reaches a position of the record Rn, and it becomes a state 3, a write circuit 8 operates, and an updated data of the storage part 10 is written in a position of the record Rn by the head 5 and is continued until it becomes a state 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a storage device having a plurality of heads, particularly a storage device such as a magnetic tape, a magnetic disk, an optical disk, etc., in which the positional relationship between the head and the storage medium is changed. The present invention relates to a storage device that performs playback and has a plurality of heads, which enables high-speed execution of a process of partially changing data that has already been stored.

(2) Prior art and problems In general, in storage devices that perform dynamic storage and playback, such as magnetic disks and magnetic tapes, data is read/played in units of bytes.
It cannot be written. Therefore, when rewriting some data, all blocks related to the data to be rewritten are read, and the read data is changed and then rewritten. At this time, since the same head is used for reading and writing, rewriting requires repositioning to match the positional relationship with the original 0 data, which takes one hour. For example, with a magnetic disk, the head does not return to the original data position until after one revolution, and with a magnetic tape, the tape must be moved in the opposite direction. This problem will be explained in more detail using the case of a magnetic disk as an example.

Figure A11 shows an example of a conventional magnetic disk, Figure lv2 shows an example of a track format, and Figure V3 shows an explanatory diagram of problems with the conventional system.

? In Figure 411, ■ is a disk, 2 is a track, which is a data storage area during one revolution of disk 1, and 3 is a track.
represents a magnetic head for reading/writing data. The recording format of the data on track 2 is structured as shown in FIG. 2, for example. Data usually consists of multiple bytes as one record, and multiple records Ro to RJ.
It is divided into and stored. Each record consists of a record address confirmation area A and a data area.

Conventionally, for example, when rewriting part of the data in record Rn, the procedure was as shown in FIG. First, a data buffer DB for the record Rn is secured in the main storage device MEM, and when the magnetic disk 3 comes to the position of the record Rn, all data of the record Rn is read into the data buffer DB. Then, the data α to be changed is rewritten into new data α on the data buffer DB and written to the original record Rn position on the disk 1. At this time, since there is only one magnetic head 3, it takes at least one rotation of the disk from reading to writing. The time for one rotation of the disk is considerably longer than a CPU cycle, since it involves one mechanical operation.

(3) Purpose of the Invention The present invention aims to solve the above-mentioned problems, and provides storage data in a storage device in which target data cannot be extracted randomly in byte units or word units.

The purpose is to enable high-speed rewriting.

(4) Structure of the Invention Therefore, the present invention prepares two heads, one for data reading and one for rewriting the changed data, and calculates the time difference in passing the same data between the two heads in read/write units. Take more than the number of bytes and update the data read by the preceding head.

Eliminates time loss in rewrites by immediately writing modified data in subsequent heads.

The time difference is reduced to the time difference in which the storage medium moves between two heads. Namely.

A storage device having a plurality of heads according to the present invention is a storage device that performs a data read operation or a data write operation in accordance with relative movement between the head and a storage medium. and a second head, and a data storage section for storing read/write data.

When rewriting data stored on a storage medium.

means for transferring data read by the first head to the data storage section; and a means for transferring the data read by the first head to the data storage section; and means for writing updated data on the data storage section to the storage medium by the second head when the position on the storage medium reaches the position of the second head. It is characterized by having the following. Referring to the following two drawings.

An explanation will be given based on an example.

(5) Embodiment of the Invention FIG. 4 is a block diagram of an embodiment of the invention, and FIG. 5 is an explanatory diagram of the operation of the embodiment of the invention.

In the figure, numerals 1 and 2 correspond to those in FIG. 1, 4 is a preceding first head, and 5 is a succeeding second head.

6 is a positioner that moves the heads 4 and 5 in the radial direction of the magnetic disk 1 and positions them on the target track 2; 7 is a read circuit; 8 is a write circuit; 9 is for reading information in the address confirmation area of the record. Lead circuit, 1
0 is a data storage unit, 11 is a record position confirmation circuit, 12
13 represents a control circuit, and 13 represents a data control circuit.

As shown in FIG. 4, a first head 4 and a second head 5 are attached in the rotational direction of the disk 1. Under the control of the control circuit 12, the lead circuit 7
reads the data on track 2 and stores it in the data storage section 10.
This is a circuit that transfers data to

If the request from the arithmetic processing unit of the host is a read request, the data storage circuit 13 transfers the read data on the data storage unit 10 to the host in response to a control signal from the control circuit 12, and also transfers the read data on the data storage unit 10 to the host. If the request from the processing device is a write request, the data transferred from the post is written into the data storage unit 1o. At this time, especially in the case of rewriting part of the data, the corresponding position in the read data previously read into the data storage unit 10 by the read circuit 7 is overwritten. The write circuit 8 is a circuit that writes data in the data storage section 10 onto the track 2 using the second head 5. The timing for writing is given by the record position confirmation circuit 11. That is, the read circuit 9 uses the second head 5 to read the address confirmation area A, and the record position confirmation circuit 1
Notify 1. The record position confirmation circuit 11 checks whether the address information notified in 1 indicates the address of the record to be written, and confirms that the second head 5 has reached the position of the record previously read by the first head 4. Once confirmed, a control signal is sent to the write circuit 8.

Next, the operation when rewriting data in the embodiment shown in FIG. 4 will be explained with reference to FIG.

For example, assume that a host processing device issues a request to write data of record Rn. As shown in state (1) in FIG. 5, the first head 4 is a record R.

When the first position of the record Rn is reached, the read circuit 7 starts a read operation, and the data of the record Rn is transferred to the data storage section 10. Then, when the first head 4 relatively moves by the length Q of the record Rn and reaches the state shown in state (2) in FIG. 5, the read operation is stopped. Next, until the second head 5 reaches the beginning position of the record Rn.

That is, while the track 2 moves by the distance shown in the figure, the data control circuit 13 changes the data of the record Rn read into the data storage section 10 in accordance with a request from the host processing device. Whether or not the second head 5 has reached the position of record Rn.

The read circuit 9 reads the address confirmation area A using the N12 head 5, and the record position confirmation circuit 11 confirms by checking whether the read address information indicates the address of the record Rn.

When it is confirmed that the second head 5 has reached the position of the record R1L, and the state is as shown in FIG. 5 (3),
The write circuit 8 operates, and the updated data in the data storage section 10 is transferred to the 9-year-old 2 head 5.

It is written to the position of record Rn. This write operation continues until the state shown in FIG. 5 state (4) is reached.

As can be seen from the above explanation, the distance Ito between the first head 4 and the second head 5 is equal to the record length h and the first head 5.
It is sufficient that the length is equal to or longer than the time required to process the data read by the head 4 plus the distance 2□' traveled by the storage medium.

In the explanation of the above embodiment, the case where only one record is rewritten has been explained, but the present invention is not limited to this, and it is also possible to continuously rewrite records on the same track one after another. can. That is, in FIG. 4, the preceding first head 4 reads the records passing one after another and buffers them in the data storage section 10. The data control circuit 13 updates the record that needs to be rewritten on the data storage unit 10, and
The control circuit 12 may be used to cause the heads 5 to write one after another. According to this, the rewritten data sections scattered on the track are rewritten one after another, so there is no need to prepare a large data storage section 10 for temporarily storing data. By conventional method.

In order to process the rewritten data scattered on the track for one round in the minimum time, a huge memory for 1 time is required, but the present invention has a great advantage from this point as well.

Although the above description has been made using a magnetic disk as an example, it goes without saying that the invention can be similarly applied to any storage device in which reading and writing are performed by a head, such as a magnetic drum device.

(6) As described in detail, according to the present invention, data change processing time in a sequential read/write type storage device is reduced.
This can be reduced to the time difference in which the storage medium moves between two heads. If the unit data size of the block to be processed is sufficiently small and the distance between the two heads is accordingly close.

can perform data rewrite processing almost instantaneously. It was. The buffer for rewriting processing is completed even when rewriting one round of a track.

It does not require a large size and can be processed at high speed.

[Brief explanation of drawings]

Figure 1 shows an example of a conventional magnetic disk, and Figure 2 shows an example of a track.
An example of the format, Figure 3 is a diagram explaining the problems of the conventional method,
FIG. 4 is a block diagram of an embodiment of the present invention, and FIG. 5 is an explanatory diagram of the operation of the embodiment of the present invention. In the figure, 1 is a disk, 2 is a track, 4 is a first head, 5 is a head of tooth 2, and 7 is a read circuit. 8 is a write circuit, 9 is a read circuit, 10 is a data storage section, 11 is a record position confirmation circuit, 12 is a control circuit, 13
represents a data control circuit. Patent applicant Fujitsu Limited

Claims (1)

[Claims] In a storage device that performs a data read or write operation with relative movement between a head and a storage medium, a first head and a second head arranged in a direction in which the storage medium moves, and read/write data. and a data storage section for storing the data, and means for transferring the data read by the first head to the data storage section when rewriting the stored data on the storage medium, and a means for transferring the data read by the first head to the data storage section; means for updating data on the data storage unit until the position on the storage medium that has been generated reaches the position of the second head, and the position on the storage medium reaches the position of the second head. A storage device having a plurality of heads, comprising means for writing updated data on the data storage section to the storage medium by the second head when the data storage section is updated.