JPS6356873A - Read system in duplicated file - Google Patents

Abstract

PURPOSE:To contrive to decrease the average read time by issuing a read request to a magnetic disk device having no load when one device has a load while the other has no load and issuing a read request to a magnetic disk device closest to a magnetic head position when both devices have no load. CONSTITUTION:A duplicated file read control means 15 discriminates the load state of magnetic disks 2, 3 detected by load state detection means 13, 14 and when it is discriminated that the both have no load, a read request is set to a read request issuing means of a magnetic disk device closest to the magnetic head at present. Thus, the read minimizing the seek time is applied. On the other hand, when any of the load state detection means 13, 14, e.g., the load state detection means 13 has a load of the magnetic disk device 2, the duplicated file read control means 15 sends the read request to the read request issuing means 17 of the magnetic disk device 3 detected to have no load. Since a read request issuing means 17 does not await the read request in this case, the read request is issued immediately and quick read is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for reading duplicated files having the same content stored on separate magnetic disk devices, and in particular to a method for reading duplicated files that can shorten the reading time. Regarding the reading method.

[Conventional technology]

Generally, in order to improve reliability and operability, files with the same content are stored on separate magnetic disk drives to create duplicate files. When reading, conventionally,
Until a failure occurs in the magnetic disk device or magnetic disk medium, a method has been adopted in which reading is performed from only one of the files, or each file is read alternately.

[Problem that the invention seeks to solve]

The conventional duplex file reading method described above does not take into account the load status of each magnetic disk device or the head position of the magnetic disk device, so the input request is issued to a magnetic disk device with a high load and the request waits for a long time. This has the disadvantage that the average reading time increases because reading is performed from a magnetic disk device located at a head position far from the requested reading position, and it takes time to move the head.

The present invention solves these conventional drawbacks, and its purpose is to provide a duplex file reading method that can shorten the reading time as much as possible.

Means for Solving Problem c] In order to achieve the above object, the present invention provides a method for reading a duplex file consisting of two files with the same content stored on separate magnetic disks. duplex file read request receiving means for accepting read requests; load state detection means for detecting the load state of each magnetic disk device; and head position detection means for detecting the current position of the magnetic head of each magnetic disk device. and if any of the magnetic disk drives is detected to be unloaded by the load state detection means, the read request received by the duplex file read request receiving means and to be executed next is sent to the head position detection means. The head position detected by the means is issued to the magnetic disk drive closer to the input destination cylinder address of the read request to be executed, and the load state detection means determines that only one magnetic disk drive is unloaded. If detected, the control means is provided for issuing a read request received by the duplexed file read request receiving means and to be executed next to the magnetic disk device detected to be unloaded.

[Effect]

When a duplex file read request is received by the duplex file read request receiving means, the control means checks the load status C of each magnetic disk drive using the detection means, and if both are unloaded, detects the head position. The head position of each magnetic disk drive is checked by means, and a read request is issued to the magnetic disk drive whose head position is closest to the cylinder address of the read request destination. Issues a read request to the magnetic disk device.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which 1 is a human control device, 2.3 is a magnetic disk device, and 4 is a memory. Duplicated files 2a and 3a having the same content are stored in the magnetic disk device 2.3. In addition, in the human control system, there is a duplex file read request receiving means IO that receives a duplex file read request from a job or task running on a central processing unit (not shown), and a magnetic head of the magnetic disk device 2.3. Head position detection means 11.1 for detecting the cylinder address where the head is placed
2, a read request issuing unit 16 that accepts a read request to the magnetic disk device 2, stores it in a queue, and issues a read request to the magnetic disk device 2, and a magnetic disk device 3.
A read request issuing means 17 accepts a read request for the magnetic disk drive 2 , stores it in a queue, and issues a read request to the magnetic disk drive 3 based on the number of waiting read requests existing in the read request issuing means 16 . The load state detection means 13 detects the load state, and the magnetic disk device 3 based on the number of waiting read requests existing in the read request issuing means 17.
When a read request to be executed next is issued from the duplex file read request receiving means 10, the load state detecting means 14 detects the load state of the load state detecting means 13, 14. Selects the magnetic disk device that issues the read request based on the detection information of the head position detection means 11 and 12, and also transfers the data read from the files 2a and 3a of the magnetic disk device to the memory 4 such as the main storage device. The duplex file read control means 15 includes a duplex file read control means 15 for controlling the duplex file reading.

In FIG. 1, when a duplex file read request is received by duplex file read request receiving means 10, this request is passed to duplex file read control means 15. When the duplex file reading control means 15 receives a reading request,
First, the load state of each magnetic disk device 2.3 detected by the load state detection means 13.14 is determined. When it is determined that all magnetic disk drives 2.3 are under no load, the current cylinder address of the magnetic head of the magnetic disk drive 2.3 detected by the head position detection means 11.12 and the request are received. The read request is compared with the input destination cylinder address, and the read request is sent to the read request issuing means of the magnetic disk device that has a cylinder address close to the input destination cylinder address. For example, if the current cylinder address of the magnetic disk device 2 is closer to the read request destination cylinder address, the read request is sent to the read request issuing means 16, and since there is no request waiting, the read request issuing means 16 immediately issues the read request. A read request is issued to the magnetic disk device 2.

Therefore, reading is performed such that the seek time is the shortest, and the read data of the file 2a is transferred to the memory 4 via the duplex file reading control means 15.

On the other hand, only one of the load state detection means 13 or 14, for example, the load state detection means 13, detects that there is a load on the magnetic disk drive 2, and the other load state detection means 13 detects that there is no load on the magnetic disk drive 3. If this is detected, the duplex file reading control means 15 issues a read request issuing means 1 of the magnetic disk device 3 detected to be unloaded.
Send a read request to 7.

In this case, the read request issuing means 17 is not waiting for a read request, so the read request is immediately issued to the magnetic disk device 3, and prompt reading becomes possible.

Note that if both the loaded RM detection means 13.14 detect that there is a load on each magnetic disk device 2.3, the read request is processed by an arbitrary method.

For example, a read request may be sent to the read request issuing means of a magnetic disk device with a light load, and the duplex file read request receiving means IO or duplex file read control may be sent to the read request issuing means of a magnetic disk device with a light load, and the duplex file read request receiving means IO or duplex file read control may be sent to the read request issuing means of a magnetic disk device with a light load. The read request may be made to wait by the means 15, and the read request may be issued to an unloaded magnetic disk device when it appears.

〔Effect of the invention〕

As explained above, according to the present invention, if one is loaded and the other is unloaded, a read request is issued to the unloaded magnetic disk device, and if both are unloaded, the magnetic head position is Since the read request is issued to the nearest magnetic disk device, the average read time can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the invention. In the figure, 1...input control device, 2.3...magnetic disk device, 2a, 3a...duplicated file, 4...memory, 10...duplicated file read request receiving means, 11 .12...Head position detection means, 13
．． 14... Load state detection means, 15... Duplicated file reading control means, 16.17... Reading request issuing means. FIG. 1 is a schematic diagram of an embodiment of the present invention.

Claims (1)

[Scope of Claims] A method for reading a duplexed file consisting of two files with the same content stored on separate magnetic disk devices, comprising a duplexed file read request receiving means for accepting a read request for the duplexed file, and a duplexed file read request receiving means for each magnetic disk. load state detection means for detecting the load state of the device; head position detection means for detecting the current position of the magnetic head of each magnetic disk drive; and head position detection means for detecting the current position of the magnetic head of each magnetic disk drive; If the load is detected, the read request received by the duplex file read request receiving means and to be executed next is input to the read request to be executed based on the head position detected by the head position detecting means. The request is issued to the magnetic disk drive that is closer to the destination cylinder address, and if the load state detection means detects that only one magnetic disk drive is not loaded, the request is received by the duplex file read request receiving means. 1. A method for reading a duplexed file, comprising: control means for issuing a read request to be executed next to the magnetic disk device detected to be unloaded.