Data reading method and data reading apparatus
a data reading and data technology, applied in the field of data reading methods and data reading apparatuses, can solve the problems of not being able to positively determine whether the resultant read data is read, improper data may not be obtained, and not being able to obtain proper data, so as to achieve easy and positive determination, and positive improvement of reliability of data reading in data storage systems
Inactive Publication Date: 2007-09-20
FUJITSU LTD
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AI Technical Summary
Benefits of technology
[0014]A configuration is made such that the flag thus attached to the reading request is kept after the issuance thereof, and read data obtained responsive to the reading request should have the same flag. Thereby, it is possible to easily and positively determine whether or not the reading data received is one responsive to the latest reading request, by reading the flag which the received read data has.
[0015]Since it is possible to easily and positively determine whether or not the read data received is one responsive to the latest reading request by reading the flag which the received read data has as mentioned above, proper data reading can be always ensured even when such an interface system as that an order of read data responsive to respective reading requests is not guaranteed as the above-mentioned PCI-Express system. Thus, reliability in data reading in a data storage system can be positively improved.
Problems solved by technology
Therefore, when a reading request is issued again after time out is detected as mentioned above (referred to as ‘retry’ hereinafter), it may not be possible to determine whether the resultant read data is one responsive to the first reading request or one responsive to the second reading request (retry) issued after the time out detection.
In such a case, since the retry is made once acquisition of read data responsive to the first reading request is given up, a problem may occur when read data is then obtained responsive to the first reading request unexpectedly after the retry, and it is not possible to positively determine whether the read data thus obtained is one responsive to the first reading request or one responsive to the retry.
In such a case, proper data may not be obtained, in view of the entire read data obtained responsive to predetermined successive reading requests.
Method used
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[0027]An embodiment of the present invention is described in detail with reference to figures.
[0028]FIG. 1 shows a configuration of a file control system according to the embodiment of the present invention.
[0029]In this file control system, a so-called RAIDx configuration such that the above-mentioned PCI-Express interface is employed as inter-device interface is provided.
[0030]In FIG. 1, respective central modules 10-0, 10-1, 10-2, . . . , 10-n and 10-m are connected mutually by means of a router 20 in such a manner that they can mutually communicate data.
[0031]To each central module, a host (H0 for the central module 10-0) and a hard disk drive (D0 for the same) by means of a device controller (DC0 for the same), are connected.
[0032]Further, each control module has a CPU 1, a memory controller hub (abbreviated as MCH, hereinafter) 2, a memory 4 and a DMA controller 3.
[0033]With reference to FIGS. 2-4, a data transfer operation example in the file control system is described next....
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A data reading method includes the steps of: a reading request issuing step of issuing a reading request for reading predetermined stored data; and a reading request re-issuing step of re-issuing a reading request when read data responsive to the reading request has not arrived within a predetermined time period, wherein: in the reading request re-issuing step, a flag is attached to the re-reading request, and thus, the re-reading request is differed from the first issued reading request.
Description
BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a data reading method and a data reading apparatus, and, in particular, to a data reading method and a data reading apparatus in which desired read data, stored previously, is obtained in response to issuance of a reading request.[0003]2. Description of the Related Art[0004]For example, a system called PCI-Express has been proposed as an interface system used when data stored in a hard disk drive is read.[0005]PCI-Express was proposed by Intel Corporation, and creation of a specification thereof has been carried on by PCI-SIG. PCI-Express corresponds to a serial interface known by a name ‘3GIO (3rd generation I / O)’.[0006]A PCI bus employed by the most of current computers applies a parallel transfer system. Thereby, no compatibility exists between the current PCI and the above-mentioned PCI-Express on the physical technical level. However, a communication protocol and so forth can be app...
Claims
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Login to View More IPC IPC(8): G06F3/00
CPCG06F3/0601G06F2003/0692G06F13/28G06F3/0673
Inventor HANAOKA, YUJIMATSUMOTO, HIDENORI
Owner FUJITSU LTD