JPH06208512A - Virtual disk device - Google Patents

Abstract

PURPOSE:To provide the virtual disk device which is easily controlled and can perform the same high-speed access with an actual machine. CONSTITUTION:A virtual disk device image file 4 is generated on a disk device 3 as a file that a host computer controls as usual. The host computer, therefore, holds file control information on the image file 4 and a virtual computer generates a mapping table 6 on a main storage device on the basis of this file control information, e.g. file allocation table, etc. The mapping table 6 contains, for example, actual cluster numbers of a disk device corresponding to cluster numbers of the virtual disk device. The virtual computer obtains addresses in storage units of the image file 4 by referring to the mapping table to access the image file, i.e., virtual disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a virtual disk device, and more particularly to a virtual disk device for operating a virtual computer on a host computer.

[0002]

2. Description of the Related Art Conventionally, as a method for realizing a virtual disk device (disk device of a virtual computer) on a host computer, there has been a system as shown in FIG. 4 or 5. (In the following description, in order to make it easier to read, the abbreviation is shown in parentheses after the name, and the abbreviation is used as appropriate.) 1) First, in the method of FIG. 4, the disk device (real disk) 102 of the host computer 101 On the host computer 101
A virtual disk device image file (image file) 103 is generated as a manageable file of the virtual computer 104, and the virtual computer 104 is the file control mechanism 1 of the host computer 101.
The virtual disk device, that is, the image file 103 is accessed through 05 to 107. 2) In the method of FIG. 5, a special disk device image area 201 is set on the real disk 102 of the host computer 101.
Is installed and the contents are made invisible from the host computer 101, and the input / output control mechanism 202 for the virtual computer 104 is entrusted with the management in this area 201.

[0003]

The advantages of the method 1) are as follows.
The image file 103 can be managed from the host computer 101 side, and therefore, no special mechanism is required on the virtual computer 104 side to maintain and manage the image file 103. However, the disadvantage of this method is that the disk access is performed via the file control mechanisms 105 to 107 of the host computer 101, so that the access speed is lower than that of the actual machine and the error in the processing speed becomes large. On the other hand, the advantage of the method 2) is that the disk can be accessed at the same speed as the actual machine. However, a drawback of this method is that a dedicated mechanism (program) 202 or the like is required to control the input / output of the disk device image area 201, and therefore maintenance is troublesome. Another conventional technique relating to input / output of a virtual computer is disclosed in Japanese Patent Laid-Open No. 1-209538. According to this technique, when a new peripheral device is required for the virtual computer, the peripheral device can be added without modifying the monitor program of the virtual computer. However, with this technology, it is not possible to eliminate the two contradictory drawbacks that we are discussing here. In addition, there is no other conventional technique that can solve this drawback. The purpose of the present invention is to
It is an object of the present invention to solve these drawbacks of the prior art at the same time, and to provide a virtual disk device which can be easily managed and can be accessed at the same high speed as a real machine.

[0004]

To achieve the above object, according to the present invention, a virtual disk device image file created on a disk device as a file managed by the host computer, and the host computer with respect to the virtual disk device image file A mapping table that is generated on the main storage device by the virtual computer based on the file management information that it holds and that holds the address of the storage unit of the virtual disk device image file to the address of the storage unit of the virtual disk device; The virtual computer refers to the mapping table to obtain the storage unit address of the virtual disk device image file corresponding to the storage unit of the virtual disk device, and accesses the virtual disk device image file by the address.

[0005]

The virtual disk device image file is created on the disk device as a file managed by the host computer as in the case of the above-mentioned conventional technique 1). Therefore, the host computer holds the file management information about this image file. The virtual computer creates a mapping table on the main storage device based on the file management information, for example, the directory information and the file allocation table. The mapping table holds the address of the storage unit of the image file with respect to the address of the storage unit of the virtual disk device, for example, the actual cluster number with respect to the cluster number of the virtual disk device. The virtual computer refers to the mapping table to obtain the address of the storage unit of the image file corresponding to the storage unit of the virtual disk device, and accesses the image file, that is, the virtual disk device by this address. That is, the virtual computer accesses the disk device image file using only the low-level I / O control mechanism of the host computer. Therefore, as in the case of the above-mentioned conventional technique 2), high-speed access similar to that of an actual machine is possible.
On the other hand, since the virtual disk device image is generated as a file managed by the host computer, a dedicated program for input / output control, such as reference numeral 202 of the prior art 2), is not required and can be easily Can be maintained.

[0006]

The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows the configuration of the embodiment. In the figure, reference numeral 1 is a virtual computer which operates on the host computer 2. 3 is a disk device (real disk) of the host computer, 4 is a virtual disk device image file (image file), and this image file 4 is generated on the real disk 3 as a file managed by the host computer 2. Reference numeral 5 is file management information for each file stored in the real disk 3, starting with the image file 4, the file name, the head cluster number (the head cluster number of the cluster storing the file), the creation date and other information. Holds information for file management. 6 is a mapping table, an example of which is shown in FIG. This table 6 is generated by the virtual computer 1 and holds the cluster number of the real disk 3 with respect to the cluster number of the virtual disk device (virtual disk). The virtual computer 1 reads the actual cluster number from this table, and the host computer It is accessed using the lower I / O control mechanism 7 of 2.

The virtual disk cluster (FIG. 2) is literally virtual, and its size and number are arbitrarily determined when the virtual computer 1 is set. However, this virtual disk cluster is actually realized on the image file 4. That is, it is assumed that the cluster size of the virtual disk is set to 2 kilobytes and the number is set to 32768 (FIG. 2). The product of both ≈ 65 megabytes is the total storage capacity of the virtual disk, and the image file 4 is the real disk 3
Generated at this size on top. This image file 4
Is divided into 2 kilobytes from the beginning, which corresponds to each cluster of the virtual disk. In the example of FIG. 2, one cluster of the real disk 3 corresponds to one cluster of the virtual disk. Therefore, the cluster size of the real disk 3 and the cluster size of the virtual disk are equal (for example, 2 kilobytes each).

It should be noted that, for example, there are four virtual disk clusters.
In the case where the cluster of the real disk 3 is 2 kilobytes while the size of the real disk 3 is 2 kilobytes, two clusters of the real disk 3 are allocated to one cluster of the virtual disk. In the opposite case, one cluster of real disk 3 is assigned to two clusters of virtual disks. In this case, information on which part (first half, second half, etc.) of the cluster of the real disk 3 the cluster of the virtual computer 1 corresponds to is also added. FIG. 3 shows a configuration example of the real disk 3. The DIR is a directory, which holds information such as the name of the file stored in the real disk 3 and the start cluster number of the file (the number of the first cluster in the cluster group storing the file). FAT is a file allocation table and has a data storage area DA corresponding to each cluster 31 (reference numerals DA and 31 are only partially displayed). The number above the data storage area DA is the number of that area and corresponds to the cluster of that number. The directory DIR and the file allocation table FAT correspond to the file management information 5 in FIG.

The operation of this embodiment will be described. Prior to the input / output operation of the virtual disk, the virtual computer 1 reads the file management information regarding the image file 4 (= virtual disk) from the file management information 5 via the host computer 2 (FIG. 1A, B). . The virtual computer 1 uses the read file management information to create an image file 4
The map pig table 6 is assembled and stored in the main storage device (not shown) assigned to the virtual computer 1. When the virtual computer 1 inputs / outputs to / from the virtual disk, the low-level input / output control mechanism 7 of the host computer 2 is directly used to access the virtual disk (image file 4) based on the mapping table 6. (Fig. 1C,
D).

A specific example will be given. The directory DIR
Is expressed only by "DIR", and the file allocation table FAT is expressed only by "FAT". For example, assume that the name of the image file 4 at this time is "IMGFILE" shown in the DIR of FIG. The start cluster number “125600” is obtained from the directory information of this image file IMGFILE. The starting cluster number represents the beginning of the cluster group in which the file is stored. This number is stored in the mapping table 6 as the cluster number of the real disk 3 corresponding to the cluster number “0” of the virtual disk (FIG. 2). The number of the next cluster that stores the image file IMGFILE is the data area DA corresponding to the start cluster, that is, 12560.
It is stored in the 0th data area DA. The contents of this data area DA are referred to. In the example of FIG.
The cluster number "1" is stored. Similarly, this cluster number is stored in the mapping table 6 as the cluster number of the real disk 3 corresponding to the cluster number “1” of the virtual disk.

In the same manner, the cluster number of the real disk 3 corresponding to the cluster number of the virtual disk is sequentially obtained and stored in the mapping table 6. When the value stored in the data storage area DA of the FAT is a predetermined value, for example, “FFF8H to FFFFH”, the cluster 31 is the last cluster that stores this image file IMGFILE. This completes the storage of the cluster number of the real disk 3 in the mapping table 6. The mapping table 6 is stored in the virtual computer 1 as described above.
Stored in the main storage device (not shown) assigned to. When inputting / outputting to / from the virtual disk (image file 4), the cluster number of the real disk 3 is obtained by referring to the mapping table 6, and the cluster 31 is directly used by using the input / output control mechanism 7 of the host computer 2. To access.

[0012]

As described above, according to the present invention, a virtual disk device image file is created on a disk device as a file managed by the host computer, and the virtual disk device image file is based on the file management information held by the host computer. In addition, the virtual computer generates a mapping table on the main storage device, which holds the address of the storage unit of the image file with respect to the address of the storage unit of the virtual disk device, and the virtual computer refers to this mapping table to create a virtual table. The storage unit address of the image file corresponding to the storage unit of the disk device is acquired, and the virtual disk device image file is accessed by the address. Therefore, the virtual computer can access the disk device image file only by using the low-level I / O control mechanism of the host computer, and the high-speed access as in the actual device can be achieved as in the prior art 2). On the other hand, a dedicated program for input / output control, such as reference numeral 202 of the prior art 2), is not required, and maintenance can be easily performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a mapping table.

FIG. 3 is a diagram showing an example of a configuration of a disk device.

FIG. 4 is a diagram showing a configuration example (1) of a conventional virtual disk device.

FIG. 5 is a diagram showing a configuration example (2) of a conventional virtual disk device.

[Explanation of symbols]

 1 virtual computer 2 host computer 3 disk device 4 virtual disk device image file 5 file management information 6 mapping table

Claims (1)

[Claims] 1. A virtual disk device for operating a virtual computer on a host computer, the virtual disk device image file being created on the disk device as a file managed by the host computer, and the virtual disk device image. A file is created in the main storage device by the virtual computer based on file management information held by the host computer, and holds the address of the storage unit of the virtual disk device image file with respect to the address of the storage unit of the virtual disk device. A mapping table, the virtual computer refers to the mapping table to obtain an address of a storage unit of the virtual disk device image file corresponding to a storage unit of the virtual disk device, and the virtual disk device image is obtained from the address. File Virtual disk and wherein the accessing.