JPH0695808A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent the reduction of the apparent processing speed to a reading request by ensuring the effective functioning of a read-ahead cache even in such a case where a large amount of data are continuously transferred to the outside by the reading request. CONSTITUTION:The storage capacity of a sector buffer 8 which stores temporarily the data read out of a hard disk 5 for the transfer to a host system 2 is set at 8 megabits or more. Therefore, the function of a cache means can effectively work as long as the length of data requested by the system 2 for reading is kept within the storage capacity. Thus, it is possible to extremely reduce such a case where the lacking data of the cache means are read out of the disk 5 and sent to the buffer 8 against a reading request. Then, the apparent processing speed can be kept at the original ability level of a magnetic disk device to the reading request.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device such as a hard disk device using a 2.5-inch or 3.5-inch hard disk as a recording medium.

[0002]

2. Description of the Related Art Conventionally, looking at the form of read access to a hard disk device by an OS such as MS-DOS, about 50% of them are sequential reads. Due to the tendency of this access method, the hard disk drive is equipped with a data read-ahead function called a read-ahead cache.

This read-ahead cache has a function of reading data ahead of the data read requested by the host into the sector buffer from the disk and sending the data from the sector buffer to the host when the next read request is generated. . As a result, the response speed to the read request from the host is improved.

Further, in consideration of the current situation that the data transfer amount required for one access is 32 kilobytes or less in most cases, the area of the sector buffer is, for example, 32.
Divide into several segments by kilobyte,
In some cases, a method of storing data in multiple areas on the hard disk in a cache is used.

In most conventional OS operations, the amount of data transferred for a single read request is smaller than the size of the sector buffer. For example, in an existing 2.5-inch hard disk drive, the capacity of the sector buffer is usually 1 megabit (1 kilobyte is 1024
In the case of bytes, it is 128 kilobytes or less, whereas in most cases, the data transfer amount for one read request is 32 kilobytes or less.

However, in recent years, the capacity of the hard disk has remarkably increased, and accordingly, an operation different from the conventional usage has been required for the apparatus. For example,
When performing image processing, there is a case where image data whose data length exceeds the capacity of the sector buffer is continuously transferred to the host.

In this case, the cache function cannot sufficiently operate with the capacity of the conventional sector buffer. As an example thereof, an operation in the case where 1-megabyte data is continuously read from the hard disk device and transferred to the host system will be described with reference to FIG. In this figure, (a) shows each timing of reading data from the hard disk into the sector buffer, and (b) shows each timing of reading data from the sector buffer into the host system.

Here, the time required to read 1 megabyte of data from the hard disk into the sector buffer is 450 milliseconds, and the host system takes 1 time from the sector buffer.
The time required to read megabytes of data is 300
Millisecond, host system data read interval is 500
The milliseconds and the sector buffer size are 128 kilobytes.
In the first read request, since there is no data in the sector buffer, the data is transferred from the hard disk to the sector buffer in the period Ta and the data is transferred to the host system in the period Tb.

When all the target data is read from the hard disk into the sector buffer, a process of reading data ahead of the read-requested data into the sector buffer is performed during the Tc period as a cache operation. At this time, the data already read into the sector buffer becomes unnecessary after the transfer to the host system is completed, and the data for the cache is successively written in the released area. Then, this processing operation ends when the cache data fills the area of the sector buffer. On the other hand, when the data transfer to the host system is completed, the process for the next read request is started with the data read interval Td interposed, and the cache data held in the sector buffer during the Te period is read into the host system.

However, the data held in the sector buffer at this time is only a part of all the read request data. Therefore, as for the shortage, similar to the processing for the first read request, data is once read from the hard disk into the sector buffer and transferred to the host during the Tf period.

At this time, since the data read speed from the hard disk to the sector buffer is slower than the data transfer speed to the host system, the apparent processing speed for the read request drops to a value lower than the original capacity of the device. I will end up.

[0012]

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem and enables the read-ahead cache to function effectively even when a large amount of data is continuously transferred to the outside in response to a read request. Thus, it is an object of the present invention to provide a magnetic disk device capable of preventing an apparent reduction in processing speed for a read request.

[0013]

In order to achieve the above-mentioned object, the magnetic disk device of the present invention has a storage means for temporarily storing the data read from the disk for external transfer, and a read request from the outside. In a magnetic disk device having cache means for reading data ahead of data from the disk to the storage means and sending data from the storage means to the outside when the next read request is generated, the storage means is 8 megabits or more. It is characterized by having a storage capacity of.

[0014]

According to the present invention, the storage means has a storage capacity of 8 megabits or more, and as long as the length of the data requested to be read falls within this storage capacity, the cache means can effectively function. You can Therefore, when a read request is generated, it is possible to significantly reduce the situation where the data of the cache shortage is read from the disk to the storage unit, and it is possible to maintain the apparent processing speed for the read request at the capability level originally possessed by the device. .

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a 2.5-inch hard disk drive according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 is a hard disk device with a built-in controller, and 2 is a host system which is connected to the hard disk device 1 through an external bus 3 and requests the hard disk device 1 to write and read data. Further, in the hard disk device 1, reference numeral 4 is a hard disk controller (HDC), which communicates with the host system 2 and controls transfer of data to a sector buffer 8 which will be described later, and further from a 2.5 inch hard disk 5 which is a recording medium. Controls reading and writing of data. Reference numeral 6 denotes a CPU which controls the HDC 4 and a servo processing circuit 16 described later according to a program stored in the ROM 7. 8 is data read from the hard disk 5 and the hard disk 5
This is a sector buffer that temporarily stores the data to be written to. In this embodiment, the sector buffer 8 having a storage capacity of 8 megabits (1 megabyte) is used.

A magnetic head 9 writes and reads signals to and from the hard disk 5. 10
Is a spindle motor for rotating the hard disk 5. Reference numeral 11 is a motor control circuit for controlling the rotation speed of the spindle motor 10. Reference numeral 12 is a VCM that mounts the magnetic head 9 and moves it in the radial direction of the hard disk 5.
A carriage mechanism including a (voice coil motor).
A VCM driver 13 drives and controls the VCM. 1
Reference numeral 4 denotes a signal processing circuit, which processes the position signal read from the hard disk 5 and adds it to the servo processing circuit 16.
Output to. A carriage control circuit 15 controls the VCM driver 13 according to an instruction from the servo processing circuit 16. Reference numeral 16 denotes a servo processing circuit, which is position information input from the signal processing circuit 14 and the carriage control circuit 15
Control information is sent to the CPU 6, and the carriage control circuit 15 is controlled according to an instruction from the CPU 6. 17 is RLL
EN (encoder) / DEC (decoder), HD
The NRZ encoded data input from C3 is converted into a write signal for the magnetic head, and the signal read from the hard disk 5 is NRZ encoded and sent to the HDC 4.

Next, a typical operation of the 2.5-inch hard disk drive of this embodiment will be described.

FIG. 2 is a timing chart for explaining the operation in the case where 1 megabyte of data is continuously read from the hard disk device 1 and transferred to the host system 2. In this figure, (a) shows the hard disk 5
Shows the timing of reading data from the sector buffer 8 to the sector system 8 and (b) shows the timing of reading data from the sector buffer 8 to the host system 2.

Here, the time required to read 1 megabyte of data from the hard disk 5 into the sector buffer 8 is 450 milliseconds, and the time required for the host system 2 to read 1 megabyte of data from the sector buffer 8 is 300 milliseconds. The data reading interval of the host system 2 is 500 milliseconds.

At the first read request, the sector buffer 8
Since there is no data in, while reading data from the hard disk 5 to the sector buffer 8 during the Ta period,
Data is transferred to the host system 2 in the Tb period.

When all the target data is read from the hard disk 5 into the sector buffer 8, a process of reading the data ahead of the read-requested data into the sector buffer 8 is performed during the Tc period as a cache operation. At this time, the data already read in the sector buffer 8 becomes unnecessary after the transfer to the host system 2, and the data for the cache is sequentially written in the released area. Then, this processing operation ends when the area of the sector buffer 8 is filled with cache data. Here, since the sector buffer 8 has a capacity of 8 megabits (1 megabyte), all the data requested to be read is written in the sector buffer 8.

On the other hand, when the data transfer to the host system 2 is completed, the process for the next read request is started with the data read interval Td interposed. At this time, the sector buffer 8
Since all the data that is the target of the present read request are prepared in this field, the processing for the present read request is completed by reading the data from the sector buffer 8 and transferring it to the host system 2 during the Te period. Become. At the same time, the sector buffer 8 released after the data transfer is completed
The data for the next cache is sequentially read into the area of (1) during the Tf period.

Even when the next read request is generated, all the target data has been read into the sector buffer 8. Therefore, the data transfer to the host system 2 is completed at high speed, and thereafter, continuous data is accessed. In the meantime, the above operation is repeated.

Thus, according to the hard disk device of the present embodiment, by using the sector buffer 8 having a storage capacity of 8 megabits (1 megabyte), a large amount of data is continuously transferred to the host system 2 in response to a read request. Even in such a case, the original function of the read-ahead cache can be fully exerted, and an apparent reduction in the processing speed for the read request can be suppressed.

Although the 2.5-inch hard disk device has been described in this embodiment, it goes without saying that the present invention can be applied to a hard disk device having a 3.5-inch or other disk as a recording medium.

[0028]

As described above, according to the magnetic disk device of the present invention, even if a large amount of data is continuously transferred to the outside in response to a read request, the read-ahead cache can be effectively operated and read. It is possible to prevent an apparent reduction in processing speed for a request.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a 2.5-inch hard disk device according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining an operation when 1 megabyte of data is continuously read from the hard disk device and transferred to the host system in the embodiment of FIG.

FIG. 3 is a timing chart for explaining an operation in the case where 1 MB data is continuously read from the hard disk device and transferred to the host system in the conventional hard disk device.

[Explanation of symbols]

1 ... Hard disk device, 2 ... Host system, 3 ... External bus, 4 ... Hard disk controller (HDC),
5 ... Hard disk, 6 ... CPU, 7 ... ROM, 8 ... Sector buffer, 9 ... Magnetic head, 10 ... Spindle motor, 11 ... Motor control circuit, 12 ... Carriage mechanism, 1
3 ... VCM driver, 14 ... Signal processing circuit, 15 ... Carriage control circuit, 16 ... Servo processing circuit, 17 ... RLL
-EN (encoder) / DEC (decoder).

Claims (1)

[Claims] 1. Storage means for temporarily storing data read from a disk for external transfer, and data ahead of the data requested to be read from the outside, read from the disk to the storage means, and a next read request is issued. A magnetic disk device having a cache means for sending data from the storage means to the outside when it occurs, wherein the storage means has a storage capacity of 8 megabits or more.