Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data in specific format
Patent
1996-10-23
1999-03-23
Psitos, Aristotelis
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data in specific format
360 15, 386 52, G11B 509
Patent
active
058868410
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a digital data copying apparatus for coping a large amount of sequential data particularly using a tape streamer for recording digital data on a magnetic tape.
BACKGROUND ART
At present time, as the capacity of data to be processed increases, the necessity for a data recording apparatus that records data on a magnetic tape is increasing. Unlike with a disk type recording medium, data is almost sequentially recorded on a magnetic tape type recording medium.
Now, assume an example that there are two tape streamers and that data is exchanged therebetween (for example, data is copied therebetween). As a prevailing method performed a the present time, data is copied between the two tap streamers through a host computer as shown in FIG. 20. When data is copied from a data recording device (hereinafter referred to as a device) 202 to a device 203, he host computer 200 reads data from the device 20 and stores the data to a buffer memory (not shown) of the host computer 200 through a bus 201. The host computer 200 causes the data stored in the buffer memory to be sent to the device 203 through the bus 201 and then the data to be written to a record medium of the device 203.
As another method, a protocol such as the SCSI system that has a data copy command in the command system is known. When data is copied from a device 206 to a device 205 corresponding to the protocol, as shown in FIG. 21, a host computer 204 causes a copy command to be sent to the device 205 through a SCSI bus 207. The device 205 that has received the copy command sends a read command to the device 206. Thus, data stored in the device 206 is automatically sent to the device 205 through the SCSI bus 207 and then written to a record medium of the device 205.
In the copying method using the host computer, since data is sent through the memory of the host computer, the memory resource of the computer and the CPU resource for data input/output commands are wasted. In addition, since data flows in the bus twice, the transmission rate of the data becomes around 1/2. Moreover, since the process speeds of the devices are satisfactorily high, the process speeds of data that is input/output to/from the host computer affect the data transmission speeds.
Furthermore, data is sent with an unit named a block. The block is a set of data with a predetermined size. A file is composed of a plurality of blocks. When data is sent through the host computer, the block size of the data is restricted by for example the size of the buffer memory of the host computer. Thus, the image of a data block on the copy source side becomes different from the image of a data block on the copy destination side. Consequently, an application that uses a block image of a file is adversely affected.
On the other hand, in the case that the protocol that has a data copy command in the command system as with the above-described SCSI system, the problems involved in the method using the host computer (for example, the problems of the waste of the CPU resources and the data transmission speeds) are solved. However, in this case, a block image cannot be stored as it is.
Devices that perform a copy operation are for example a block device (such as a disk unit) and a sequential device (such as a magnetic tape unit). In the block device, logical blocks of data are controlled as the conception of sectors. Thus, the block size is fixed. When data is copied between devices with the same sector length, it is not necessary to consider the block size. In other words, when data is copied between block devices such as disk units, a sector image is simply copied as in many real examples.
On the other hand, in the sequential device, data is recorded as variable length blocks. In other words, the amount of data being recorded varies block by block. As an example, 100 bytes of data, 50 bytes of data, and 1024 bytes of data are recorded in the first data block, the second data block, and the third data block, respectively. The images of blocks vary correspo
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Kikuchi Akihiro
Nishio Tsuyoshi
Frommer William S.
Psitos Aristotelis
Sony Corporation
Wamsley Patrick
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