JPH04225444A - Data buffer read/write control system - Google Patents

Abstract

PURPOSE:To attain the DMA transfer of data at a high speed by dividing a data buffer into plural segments and using one of these segment just to store the write data transferred from a host device at the time of reception of a write request. CONSTITUTION:A write data-only segment is provided to a data buffer part 3 and therefore the data once read out is never written on the data transferred with a write command even if the read commands are continuously requested by a magnetic disk device 4 together with a write command. Thus the corresponding data is stored in the part 3 for each read command and a series of data transfer operations can be smoothly carried out with no mechanical action requested to the device 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a read/write control method for a data buffer provided in a magnetic disk control device connected between a host device and a magnetic disk device, and in particular, to In a disk device, equipped with a ring buffer function, D
The present invention relates to a read/write control method for a data buffer used in MA transfer.

In recent years, with the personalization of computer systems, magnetic disk drives have also become smaller.
Magnetic disk drives, which were originally used as external storage devices, have come to be built into personal computers. In addition to the demand for smaller size, magnetic disk drives are also required to have faster data transfer speeds, and are also required to have larger capacities for image processing.

[0003] When speeding up data transfer in a magnetic disk device, the read-ahead cache function and ring buffer function are used to retain read data in the data buffer without erasing it as much as possible, thereby reducing the mechanical speed of the magnetic disk device. Technology that enables high-speed data transfer without intervening operations has already been realized. Here, the read-ahead cache function refers to the read-ahead cache function, which stores more data than the specified range from the host device (CPU) in advance into the data buffer without the intervention of the microprocessor (MPU) in the data buffer in the magnetic disk control device. This is a function that allows you to read it. Furthermore, the ring buffer function is a function that allows the address range of the data buffer to be specified endlessly as if it were an infinite loop.

0004

2. Description of the Related Art FIG. 5 is a block diagram of a data buffer section of a conventional magnetic disk control device. As shown in the figure, the data buffer section is divided into a plurality of segments 1 to 4, and the control section takes in the ring buffer function for each segment to control and manage it. That is, in the magnetic disk control device, the data read from the magnetic disk device in response to a request from the host device is stored in each segment in this data buffer unit, and once the data is read from the magnetic disk device, the data is stored in each segment. It stores the data and transfers the data in response to a request from the host device.

[0005] After this data transfer is completed, each segment of the data buffer section is pre-read by the amount specified by the host device using the read-ahead cache function and the ring buffer function. Store the data of. In this way, by pre-reading and storing the data of the magnetic disk device in each segment, when the host device reads from the magnetic disk device once and then reads the data beyond that, the magnetic disk device's mechanical Since no operation is required, data can be transferred at high speed.

[0006]

By the way, data requested from a host device to a magnetic disk device requires not only reading from the magnetic disk device but also writing to the magnetic disk device. In this case, data is transferred once to the host device for all segments 1 to 4 to the data buffer shown in FIG.

[0007] Furthermore, when pre-read data for dealing with the next read request is held by the read-ahead cache function, these pre-read data are also
The write data transferred from the host device may overwrite the pre-read data, and the pre-read data stored in order to handle the next read request may become invalid. Therefore, it is necessary to perform a mechanical operation again to read the same data from the magnetic disk device to the data buffer section, resulting in a significant drop in performance.

[0008] In this way, when the host device makes mixed read and write requests to the magnetic disk device, the data previously read from the magnetic disk device to the data buffer section is used in the next write request. will be overwritten and erased by the write data. Therefore, if there is a read request that involves mechanical operation of the magnetic disk device again, there is a risk that a significant drop in performance will occur.

An object of the present invention is to divide a data buffer section of a magnetic disk controller into a plurality of segments, designate one segment as a write-only segment,
When a write request is made from the host device, it is used only to store the write data transferred from the host device.
Data previously read from a magnetic disk device should be stored without being overwritten as much as possible,
The purpose is to speed up transfer.

0010

[Means for Solving the Problems] FIG. 1 is a diagram showing the basic configuration of the present invention. The present invention provides a data buffer provided in a magnetic disk control device that is connected between a host device and a magnetic disk device and controls data transfer between these, in which the data buffer is divided into a plurality of segments, and each segment This data buffer read/write control method uses a ring buffer function to control writing/reading of a data buffer, and as shown in the figure, one of the divided segments is allocated as a write-only segment, and the host device When a write request is made to the magnetic disk device, temporary writing is performed in this write-only segment. Then, in order to set this write-only segment in the data buffer section, the setting plug connecting the microprocessor and the control section is short-circuited.

[0011]

[Operation] According to the present invention, when a host device sends an instruction including a read request and a write request, the write data transferred due to the write request is stored in the data buffer section dedicated to the write data segment. Stored. Therefore, the number of cases in which data previously read from the magnetic disk device is overwritten by this written data is greatly reduced, and the effective utilization rate of retained data is improved.
Therefore, it is possible to speed up data transfer between the host device and the magnetic disk device. If the system has relatively more read requests than write requests, the risk of data stored in the data buffer being destroyed is extremely low even if many write commands are issued. Efficient data transfer can be achieved.

0012

Embodiment FIG. 2 is a diagram showing the configuration of an apparatus to which the present invention is applied. This figure shows the main part configuration of a magnetic disk control device. In the figure, a microprocessor (MPU) 1 controls the operation of the control unit 2 and the operation between the magnetic disk device and the host device using a microprogram. 2
is a control unit that controls the entire magnetic disk device, and in this example is composed of an LSI, and is responsible for data transfer between the data buffer unit 3 and the host device, data transfer between the magnetic disk device and the host device, and magnetic disk drive. Controls the data read from the disk device. 3 is a data buffer section composed of a plurality of segments. 4 is a magnetic disk device as an external storage device, 5 is an I/O port for inputting commands such as writing from the host device and data transfer thereof, 6 is a setting plug to be described later, and 7 is a host device (CP
U).

As mentioned above, the data buffer section 3 is divided into four segments by the control section 2, one of which is used only for storing write data, and the other three segments are used only for storing write data.
Although read data can be held in one segment, the setting plug 6 is used to set this write-only segment. Here, the host device 6 and I
/O port 5 operates in accordance with the SCSI interface standard.

FIG. 3 is a configuration diagram of caching parameters. Control of the data buffer unit divided into a plurality of segments will be explained below. This segmented buffer control is specified by MODE in the SCSI interface standard.
, SEL, and ECT command parameters. As shown in the figure, the caching parameters of the SCSI interface standard are as follows: The minimum prefetch number is the minimum number of blocks to be read from the magnetic disk device to the data buffer section when reading data in advance, and the maximum prefetch number is the number of blocks read in advance. This is the maximum number of extra blocks to be read from the magnetic disk device to the data buffer unit at a time.

[0015] The number of cache segments is a specified value for how many segments the data buffer section is divided into.
The cache segment size specifies the data size per segment. If "1" is specified in the size bit ("SIZE"), the cache segment size of the parameter is applied, and if "0" is specified in the size bit ("SIZE"), the cache segment size is applied. numbers apply.

Here, if the maximum prefetch number is specified as a value larger than the cache segment size, SCSI sense data indicating this to the host device 7 is generated as an invalid parameter specification. The magnetic disk control device uses these parameters to control the data buffer section, so as shown in the flowchart below, the host device uses these parameters in the data buffer section immediately after power-up before data transfer. It is necessary to forward it to the department.

By the way, in the setting plug shown in FIG. 2, this setting plug 6 is used to set a condition for using one segment of the data buffer section exclusively for write data. Status of this setting plug 6 (open, short circuit)
can be directly read from the MPU 1, and segment control of the data buffer is performed according to the setting state by the MPU. This setting plug also sets the SCSI standard level and the parameter processing method shown above, and also allows other settings of the magnetic disk control device.

In this case, when the configuration plug 6 is opened, the size bit of the caching parameter is set to "
0" is specified and buffer segment control is executed with the parameter specified value. When the setting plug 6 is short-circuited, "1" is specified as the size bit of the parameter and 1 of the write-only segment is set as the parameter specified value. Segment control is performed using the added value. That is, when the setting plug 6 is short-circuited, a write-only segment is set. For example, if you specify "3" as the number of cache segments,
The setting plug 6 is short-circuited to control the data buffer unit 3. In this case, since "3" is designated as the number of cache segments in the parameter, the segment configuration of the data buffer section 3 is composed of four segments in total including the write-only segment.

With such a configuration, if the host device 7 requests a read request command many times in succession,
Moreover, if a write request command is also requested during that time, the data that has been read once will not be overwritten by the data transferred by the write command, so the corresponding data will be stored in the data buffer section 3 every time a read command is issued. Since data exists, the requirement for mechanical operation of the magnetic disk device 4 is significantly reduced, and data transfer speed can be significantly improved.

On the other hand, if the setting plug 6 is left open, the write-only segment is not set, so the cache
When "3" is specified as the number of segments, three segments not including the write data-only segment are created in the data buffer section. This has the advantage that the segment size per segment is larger than when the setting plug 6 is shorted, but the rate at which data stored in each segment becomes invalid during a write operation also increases.

FIG. 4 is a processing flowchart of the present invention. First, the host device reads various parameters for setting a write-only segment from the medium when the power is turned on (step 1), and the magnetic disk control device selects MODE, S
A caching parameter is received by the ELECT command (step 2), and it is checked whether the size bit ("SIZE") of the caching parameter is "1" (step 3). Then the size bit is "1"
At this time, the data buffer section is controlled according to the value specified by the segment size of the caching parameter, and the next process is performed (step 4). On the other hand, if the size bit is "0" in step 3, it is checked whether the setting plug is shorted or open (step 5), and if it is open (plug on), the value specified by the number of segments in the caching parameter is Then, control the data buffer to perform the next process (step 6), and when there is a short circuit (plug off),
The data buffer is controlled by the number of segments in the caching parameter plus one, and the next process is performed (step 7).

[0022]

Effects of the Invention As explained above, the data buffer section can be divided into a plurality of segments, and the read ahead function and ring buffer function can be controlled for each segment.
In a magnetic disk control device using SI, if a segment dedicated to write data is provided in the data buffer section as instructed by the configuration plug, the magnetic disk device will request read commands many times in succession, and also request write commands in between. Even in such a case, the data once read will not be overwritten by the data transferred by the write command, so the corresponding data will exist in the data buffer section every time a read command is issued, and the magnetic disk drive will A series of data transfer operations can be smoothly executed without requiring any mechanical operations, making it an extremely efficient DM.
A operation becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle configuration of the present invention.

FIG. 2 is a configuration diagram of an apparatus to which the present invention is applied.

FIG. 3 is a configuration diagram of caching parameters to which the present invention is applied.

FIG. 4 is a processing flowchart of the present invention.

FIG. 5 is a configuration diagram of a conventional data buffer unit.

[Explanation of symbols]

1...Microprocessor 2...Control unit 3...Data buffer 4...Magnetic disk device 5...I/O port 6...Host device

Claims (2)

[Claims] 1. A data buffer provided in a magnetic disk control device that is connected between a host device and a magnetic disk device and controls data transfer between them, comprising:
A data buffer read/write control method that divides the data buffer into multiple segments and controls writing/reading of each segment, wherein one of the multiple divided segments is assigned as a write-only segment. A data buffer read/write method characterized in that when a write request is made from a host device to a magnetic disk device, data is temporarily written to the write-only segment.
Write control method. 2. Claim 1, further comprising a setting plug for setting the write-only segment, so that the write-only segment can be set in the data buffer when the setting plug is short-circuited. Data buffer read/write control method described in .