JP3552471B2 - Data recording / reproducing apparatus and method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data recording / reproducing apparatus and a method thereof, and more particularly to a data recording / reproducing apparatus and a method thereof capable of ensuring data continuity even during data reconstruction.
[0002]
[Prior art]
2. Description of the Related Art In recent years, devices that record and reproduce video and audio data using a randomly accessible recording and reproduction medium, such as a hard disk, instead of a sequential access recording and reproduction medium such as a tape, are becoming widespread.
[0003]
Generally, in a video recording / reproducing apparatus that requires high image quality, a required data transfer rate is high, and a large capacity is required to record long-time data. Therefore, the transfer rate is increased by operating a plurality of hard disks in parallel, and parity data is recorded so that even if one of the hard disks fails, the original data can be restored (reconstructed). Therefore, a device whose reliability is ensured is used.
[0004]
Such a data recording / reproducing apparatus is called a disk array. The details of the disk array device are discussed in A Case for Redundant Arrays of Inexpensive Disks (RAID) (AMSIGMOD (Conference, Chicago, IL), June (1988), and the details are omitted here. , Disk array devices are called RAID and are classified into five classes, RAID 1 to 5. The disk array device shown in FIG.
Is equivalent to That is, in the disk array device of FIG. 1, a plurality of (five in this example) operate in parallel to the disk array controller 2 to which input / output data 1 having a predetermined bit width such as 8 bits or 16 bits is supplied. Hard disks 3, 4, 5, 6, and 7 are connected. Among these hard disks, the hard disks 3, 4, 5, and 6 are for data recording, and input data is sorted and recorded by the disk array controller 2. The hard disk 7 is for recording only the parity calculated from each input data.
[0005]
FIG. 2 illustrates the operation of generating parity, for example, odd parity. The four data D1, D2, D3, and D4 are supplied to an exclusive OR gate 36, and parity data DP is generated. That is, parity data DP is generated such that an odd number of ｀ 1's exist at each bit position. Note that the data D1 to D4 mean respective data of the hard disks 3, 4, 5, and 6. Then, the parity data DP is recorded on the hard disk 7 of the disk array device of FIG.
[0006]
If any hard disk fails, the original data can be restored by calculating the remaining data and the parity DP, and the restored data is re-recorded on the hard disk from which the failure has been resolved. Thus, data can be reconstructed. Usually, a failed hard disk is replaced with a new one. As an example, as shown in FIG. 3, when D3 (data of the hard disk 3) among the four data D1 to D4 becomes erroneous, if it is determined that the data D3 is erroneous, an exclusive OR gate is used. By inputting non-error data D1, D2, D4, and DP to 36, original data D3 can be restored. The hard disks 3, 4, 5, 6, and 7 perform an error correction operation using an error correction code, and when an uncorrectable error occurs, the above-described error correction using the parity is performed.
[0007]
On the other hand, when such a video / audio data recording apparatus is used for broadcasting, for example, when input video data is a D2 baseband signal, a transfer rate of about 120 Mbps is required. Assuming that the effective transfer rate of hard disks per unit is about 30 Mbps, four hard disks in the disk array are required. Further, for example, if the number of channels is required to be six, 24 hard disks are required.
[0008]
Here, the effective transfer rate is the amount of data divided by the total time required to read or write a certain amount of data. It doesn't mean a good transfer rate. In addition, it is assumed that each channel reproduces or records a plurality of or the same video simultaneously from the same recording and reproducing device.
[0009]
However, it is not common to operate as many as 24 hard disks in parallel at a time. In other words, trying to operate many hard disks simultaneously at the same time increases the burden of issuing commands and managing each hard disk, which takes extra time, and as a result, The effective transfer rate is reduced, and it is difficult to secure reliability against a failure. Therefore, conventionally, the transfer rate has been increased by operating a plurality of the above disk array devices in parallel.
[0010]
[Problems to be solved by the invention]
However, in the video recording / reproducing apparatus using the conventional disk array configured as described above, even if one of the hard disks fails and the data needs to be reconstructed, Therefore, if the requested amount of data cannot be returned within a certain period of time, that is, if an operation that causes the transfer rate to be extremely low is performed, the data will be interrupted and the playback of video and audio will be interrupted. Occurs. From this point, there is a problem that the reconstruction operation cannot be performed without permission.
[0011]
On the other hand, even if the rebuilding operation is started by the operator and the rebuilding operation is started only when the performance degradation is permitted, there is no redundancy until the rebuilding operation is started. Is forced to use.
[0012]
In general, a hard disk employs a SCSI interface. According to this standard, once a command such as data reproduction or recording is issued to the hard disk, the operation is interrupted and a new command is issued. It takes time to issue and move to the next operation. Therefore, in the method in which the disk array starts the rebuilding operation on its own and a request from the operator occurs, the rebuilding operation is forcibly interrupted at that time to reproduce or record the requested data. It takes a long time from the receipt of the request until the operation is actually started, and the overall operation time is extended. Also in this method, there is a possibility that the continuity of the data cannot be secured and the continuous reproduction of the moving image or the sound cannot be performed.
[0013]
Furthermore, in a system configured to predict the delay before actually starting the operation, when the operation is delayed, the continuous reproduction of the moving image and the audio is continued by securing the continuity of the data. Therefore, a memory for storing extra data and a control circuit for the memory are also required. As a result, costs increase.
[0014]
As described above, when a data recording / reproducing device for video / audio data is configured using a disk array having a structure for ensuring reliability by having a function of reconstructing data, a failure of the hard disk causes the data to be lost. When a portion needs to be reconstructed, there is a problem that the redundancy cannot be returned to the original state without sacrificing a part of the performance.
[0015]
Accordingly, an object of the present invention is to provide a data recording / reproducing apparatus and a method thereof capable of performing a reconstructing operation in response to a data recording / reproducing request without a decrease in performance when a failure occurs in a hard disk. To provide.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is a data recording / reproducing apparatus adapted to record data on a plurality of non-linearly accessible recording media in units of time slots.
A recording and reproducing unit for recording and reproducing data on and from a plurality of recording media,
A system management controller arranged at a predetermined interval and using a system management time slot in which a command for management is arranged from a higher order,
When it is detected that the data recorded on any one of the recording media cannot be reproduced,
Control the recording / reproducing unit to reproduce data and error correction data from a reproducible recording medium, No command for management detected A data recording / reproducing apparatus comprising: a control unit configured to reconstruct data that cannot be reproduced from data from a reproducible recording medium and error correction data in a system management time slot. .
[0017]
According to a second aspect of the present invention, there is provided a data recording / reproducing method adapted to record data on a plurality of non-linearly accessible recording media in units of time slots,
The recording / reproducing unit records and reproduces data on a plurality of recording media,
The system management controller uses system management time slots that are arranged at predetermined intervals and in which commands for management are arranged from the upper level,
When it is detected that the data recorded on any one of the recording media cannot be reproduced,
Control the recording / reproducing unit to reproduce data and error correction data from a reproducible recording medium, No command for management detected A data recording / reproducing method characterized by reconstructing unreproducible data from data from a reproducible recording medium and error correction data in a system management time slot.
[0024]
According to the present invention configured as described above, a plurality of disk arrays are operated in parallel to ensure reliability, and in a video / audio data recording / reproducing apparatus in which a transfer rate during recording / reproducing is increased, Regarding the data processing block and the data transfer method of the disk array, the command and data can be transferred at the same time, and the entire apparatus operates on a predetermined schedule using an interface in which a plurality of transmission paths operate synchronously. As a result, even if a hard disk used in the disk array fails and a data rebuilding operation is required, data can be recorded from the video / audio data processing block that occurs asynchronously. Reconstruction operation can be continued without deteriorating performance in response to a reproduction request.
[0025]
Further, according to the present invention, even in slots other than the system time slots prepared in advance, the time required for the rebuilding operation is calculated by calculating the free time and performing the data rebuilding operation for an allowable amount. Can be shortened.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 4 shows an example of the configuration of a data recording / reproducing apparatus configured using the disk array according to the present invention. This data recording / reproducing apparatus is configured so that high-quality video data can be input and output simultaneously on multiple channels (for example, channel 1 to channel 6). In FIG. 4, the disk array devices 38, 39, 40, 41, 42, and 43 equipped with six serial input / outputs are configured to operate in parallel. Each of the disk array devices 38, 39, 40, 41, 42 and 43 is composed of a plurality of data recording hard disks and one parity data recording hard disk.
[0027]
In this data recording / reproducing apparatus, six video data controllers 58,..., 59 are provided, and one channel of video data is input / output to / from each of the video data controllers 58,. It is configured. In the present embodiment, this video data is described as data compressed by MPEG or the like, but may be uncompressed video data. Further, the compression method is not limited to MPEG using inter-frame correlation, but may be data compressed by various compression methods. Also, the serial / parallel (S / P) converters 46, 48, 50, 52, 54, 56 corresponding to the connected disk array devices, and the parallel / serial (P / S) converters 47, 49, 51, 53, 55, and 57 are provided.
[0028]
The serial outputs 60, 62, 64, 66, 68, 70 of the disk array devices 38 to 43 are connected to the high-speed data bus 44 via S / P converters 46, 48, 50, 52, 54, 56. Is done. The serial inputs 61, 63, 65, 67, 69, 71 of the disk array devices 38 to 43 are connected to the high-speed data bus 45 via P / S converters 47, 49, 51, 53, 55, 57. Is done. Further, there is provided a system management controller 72 capable of communicating with a higher-level administrator via a network 73. , 59, P / S converters 47, 49, 51, 53, 55, 57, S / P converters 46, 48, 50, 52, 54, 56, for system management The data processing block 37 is constituted by the controller 72. In this embodiment, a recording / reproducing block is constituted by the six disk array devices 38 to 43.
[0029]
As described above, the video data controllers 58,..., 59 share independent 48-bit data buses 44, 45 for input and output. The video data from the video data controllers 58,..., 59 is supplied to the data bus 45 as 48-bit parallel data together with command data and the like. , 57 are converted into serial data and supplied to the disk array devices 38 to 43 through serial transfer lines 61,. The video data from the disk array devices 38 to 43 is supplied as serial data along with status data to the S / P converters 46,..., 56 through serial transfer lines 60,. , And are combined into 48-bit parallel data, which are supplied to the video data controllers 58,..., 59 through the data bus 44.
[0030]
Here, since the serial transfer lines 60, ..., 70 and the serial transfer lines 61, ..., 71 are independent, data is received from the serial transfer lines at a certain moment when viewed from the disk array devices 38 to 43. The simultaneous operation of transmitting data from the serial transfer line is possible.
[0031]
FIG. 5 shows a format of data transferred by the serial transfer lines 60,..., 70 and 61,. At the head of each data, a synchronization signal 33 for setting a timing is provided. Following this synchronization signal 33, a certain amount of command data or status data 35 is transferred. The video data controllers 58,..., 59 insert commands for the disk array devices 38 to 43 into this part and transfer them. Further, the disk array devices 38 to 43 insert the status corresponding to the command and the status indicating the current status of the disk array devices 38 to 43 into this portion and transfer them to the video data controllers 58,.
[0032]
Following this command / status data, video data 35 of 1.01 seconds (30 frames) is equally divided by the number (six) of disk array devices 38 to 43, and the video data controller 58, , 59 to the disk array devices 38 to 43, and from the disk array devices 38 to 43 to the video data controllers 58, ..., 59.
[0033]
Each of the above-described disk array devices 38 to 43 is configured as shown in FIG. When data is recorded in the disk array device according to this embodiment, input data from a predetermined video data controller is supplied to the S / P converter 14 through a serial transfer line. Here, the input data is composed of a synchronization signal, command data, and video data according to the format shown in FIG. This input data is converted into parallel data by the S / P converter 14 and supplied to the recording data controller 15. When the leading synchronization signal of the input data is detected by the recording data controller 15, a fixed amount of command data following the synchronization signal is supplied to the command FIFO 11 and accumulated.
[0034]
On the other hand, video data following the command data is supplied from the recording data controller 15 to the data multiplexer 16. Hard disks 28, 29, 30, 31 for recording video data are connected to the data multiplexer 16 via memory controllers 18, 19, 20, 21 and SCSI protocol controllers (SPC) 23, 24, 25, 26. I have. A parity operation circuit 17 is connected to the data multiplexer 16, and a hard disk 32 for recording parity data is connected to the parity operation circuit 17 via a memory controller 22 and an SPC 27. The SPCs 23 to 27 are connected in series, and one end thereof is connected to the CPU 9. The data multiplexer 16 distributes video data, and the distributed video data is recorded on the hard disks 28 to 31. At this time, the parity data calculated by the parity calculation circuit 17 is recorded on the hard disk 32.
[0035]
When a series of recording operations is completed normally, the CPU 9 issues status data corresponding to the normal completion. The status data is stored in the status FIFO 10 and then supplied to the reproduction data controller 12 at a predetermined timing. In the reproduction data controller 12, a synchronization signal is generated, status data is added to the synchronization signal, and these data are supplied to the P / S converter 13. Then, the synchronization signal and the status data are converted into serial data by the P / S converter 13, and the information of the recording completion is transmitted to the corresponding video data controller through the serial transfer line.
[0036]
When data is reproduced from the disk array device according to this embodiment, first, command data for requesting reproduction is supplied from a predetermined video data controller through a serial transfer line. In accordance with the request for the command data, the video data recorded on the hard disks 28 to 31 and the parity data recorded on the hard disk 32 are read, and the video data is synthesized by the data multiplexer 16. This video data is supplied to the reproduction data controller 12. Also, the CPU 9 generates status data corresponding to the reproducing operation. The status data is stored in the status FIFO 10 and then supplied to the reproduction data controller 12 at a predetermined timing. In the reproduction data controller 12, a synchronization signal is generated, status data and video data are added to the synchronization signal, and the data is supplied to the P / S converter 13. Then, the synchronization signal, status data and video data are converted into serial data by the P / S converter 13, and output data is transmitted through a serial transfer line.
[0037]
FIG. 7 shows the timing at which the video data controllers 58,..., 59 in the data recording / reproducing apparatus according to one embodiment of the present invention transmit data to the disk array devices 38 to 43. As shown in FIG. 7, in this embodiment, the time T seconds, for example, the time of 1.01 seconds for 30 frames of video data, is divided into time slots corresponding to the video data controller to be connected. Is assigned to one video data controller. Thus, the video data controllers 58,..., 59 are controlled so that the disk array devices 38 to 43 do not simultaneously request data recording / reproduction.
[0038]
For example, when the video data controller 1 (six video controllers 58,..., 59 are referred to as video controller 1, video controller 2,. In the specified time slot, the video data of 1.01 second (30 frames) previously stored in the memory is passed through the serial transfer line S-IN (61, 63,..., 71) to the disk array device 38. To the 43 side. At this time, following the synchronization signal and the command C1, each of the disk array devices 38 to 43 has the same amount of video data as 1.01 seconds of video data equally divided by the number of disk array devices (in this case, six). Data W1 is transferred through the serial transfer line. Here, the command C1 is a command requesting that the video data transferred following the command C1 be recorded on the hard disk in the disk array devices 38 to 43.
[0039]
In the disk array devices 38 to 43, after the input data is converted to parallel data by the S / P converter 14, the leading SYNC signal 33 (see FIG. 5) is detected, and the subsequent command C1 is sent to the recording data controller. 15 and is stored in the command FIFO 11. Further, the subsequent video data W1 is distributed and recorded by the data multiplexer 16 to each of the hard disks 28 to 31, and at the same time, the parity data calculated by the parity operation circuit 17 is recorded on the hard disk 32. When these operations are completed normally, a status S1 indicating a normal completion is added to the synchronization signal to notify the video data controller 1 through the serial transfer lines S-OUT (60, 62,. The operation is completed.
[0040]
Also, when there is a data reproduction request from the video data controller, the data is read from each of the hard disks 28 to 31 and unified by the data multiplexer 16 in reverse to the writing, and the SYNC signal 33 and the status data 34 After being converted to serial data by the P / S converter 13 via the reproduction data controller 12, the data is transferred by the transfer lines 60, 62, 64, 66, 68, 70.
[0041]
For example, when the video data controller 4 reproduces the video data R4 recorded in the disk array devices 38 to 43, the video data controller 4 sends the video data R4 to the disk array devices 38 to 43 by a command C4. Request playback of R4. When this request is issued, the video data R4 distributed and recorded on the hard disks 28 to 31 of the respective disk array devices 38 to 43 are read out on the respective disk array devices 38 to 43 side. Conversely, the video data R4 is unified by the data multiplexer 16 and the video data R4 is added to the synchronization signal and the status S4. Then, the video data R4 passes through the reproduction data controller 12 and the P / S converter 13 and passes through the serial transfer line S-OUT. Forward. The transferred data is converted into parallel data by the S / P converters 46, 48,..., 56, and received by the video data controller 4.
[0042]
In the above-described configuration, since the command and the data are simultaneously transmitted in a fixed format, the circuit of the interface part is simple, and the video data controllers 58,... The exchange of video data / command / status is performed in the time allocated in the above-mentioned time slot. Therefore, arbitration work for preventing a plurality of controllers from issuing commands at the same time or a specific controller intensively is unnecessary, control can be simplified, and a predetermined schedule is used. Since it is operating, the idle time in the disk array device can be managed.
[0043]
In one embodiment of the present invention, this free time is detected, the amount of reconstructed data that can be executed is determined, and the reconstructing operation is performed in a divided manner, so that the reconstructing operation can be performed while minimizing performance degradation. finish. The data reconstructing operation is an operation of recalculating the original data from the remaining data as described above and recording it on the hard disk from which the data has been lost. Therefore, a time Xa for the hard disk to seek the remaining data, a time Xb for reading the data, a time Xc for calculating the reconstructed data by the parity operation circuit 17, and a time for sending the status to the SPC. The sum of Xd and (Xa + Xb + Xc + Xd) is needed for the calculation of the reconstruction data. Further, it is necessary to accumulate the reconstructed data in the memory controllers 18 to 22 and record the data on the hard disk to be reconstructed. For example, when reconstructing data on the hard disk 31, the reconstructed data is stored in the memory controller 21, and then the data is recorded on the hard disk 31 in the remaining time.
[0044]
FIGS. 8, 9 and 10 show examples of the first, second and third operation timings of the data reconstructing operation according to the present invention. These timing diagrams show the internal operation of the hard disks 28 to 32 and the state of the SCSI bus between the hard disks and the SPCs 23 to 27. In the first example shown in FIG. 8, a data reconstructing operation is performed using a system time slot Ts provided for the system management controller 72. The time slots Ts are arranged at regular intervals. In the time slot Ts, a data reconstructing operation and a reconstructed data recording operation are performed.
[0045]
For example, if a failure occurs in the hard disk 31, communication between the SPC 26 and the hard disk 31 becomes impossible, and the CPU 9 detects this and disconnects the hard disk 31. Then, as shown in an enlarged manner in FIG. 8, the SPCs 23, 24, 25 and 27 send commands, and each of the hard disks 28, 29, 30 and 32 interprets the commands and executes the commands. Thereafter, a seek operation is performed, and a rotation waiting state is set. Until this state is reached, time Xa is required. At the next time Xb, the data is reproduced. The reproduced data is transferred to the SPCs 23, 24, 25, and 27 at the time Xc, and the parity is calculated by the parity operation circuit 17 at the time Xc. At the next time Xd, the status is sent to SPCs 23, 24, 25 and 27. Data reconstruction is performed according to the time of Xa + Xb + Xc + Xd.
[0046]
Next, the reconstructed data is recorded on the hard disk 31. This recording operation is also performed by a sequence consisting of transmission of a command from the SPC 26 to the hard disk 31, seeking, rotation waiting, recording of data, transfer of data to the SPC 26, and transmission of status to the SPC 26, similarly to the data reconstructing operation. You.
[0047]
The method using the time slots for the system shown in FIG. 8 does not degrade the performance as viewed from each video controller, and can reconstruct data while responding to a data recording / reproducing request. In this case, it is detected that the slot is a system slot and that there is no command for management from the host, and the amount of data that can be reconstructed within one time slot is reconstructed. The CPU 9 manages the idle time, and is configured to automatically start a rebuild operation in a system slot satisfying the above conditions. As a result, it is possible to reduce the time for reconstructing the data of the entire failed area.
[0048]
In the second example shown in FIG. 9, the data reconstructing operation is performed using the remaining time Xe after executing the command from the host system (specifically, the video data controller) in one time slot. Things. That is, when each hard disk returns an operation completion status to the SPCs 23 to 27, the CPU 9 in the disk array calculates the remaining time Xe in the time slot and calculates the number of reconstructed data that can be executed during that time. Execute. This calculation is possible from the remaining time, the data transfer rate, and the time required for access. As in the first example, the reconstruction operation is performed by reconstructing the data and recording the reconstructed data. Also, the CPU 9 manages the idle time and automatically starts the rebuilding operation.
[0049]
In the third example shown in FIG. 10, the CPU 9 in the disk array detects that no command is received from the video data controller in the assigned time slot, and calculates the number of reconstructed data that can be executed in the time slot. To do. This calculation is possible based on the amount of data that can be accessed within one time slot and the time required for access, and can be set as a predetermined data amount as in the case of the system slot. Further, similarly to the first and second examples, the CPU 9 automatically starts the rebuilding operation in the idle time.
[0050]
As described above, one embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. For example, data to be recorded and reproduced may be a mixture of video data and audio data. Further, as the redundant data for error correction, an error correction code other than the parity may be used.
[0051]
【The invention's effect】
As described above, according to the present invention, in a video / audio data recording / reproducing apparatus in which a plurality of disk arrays are operated in parallel to ensure reliability and a transfer rate during recording / reproducing is increased, Regarding the data transfer method of the processing block and the disk array, the command and data can be transferred at the same time, and the entire apparatus operates on a predetermined schedule using an interface in which a plurality of transmission paths operate synchronously. And even if a failure occurs in the hard disk used in the disk array and the data must be rebuilt, the data recording / reproduction request from the data processing block generated asynchronously On the other hand, the reconstruction operation can be continued without lowering the performance.
[0052]
Further, according to the present invention, even in a slot other than the system time slot prepared in advance, the idle time is calculated, and the data reconstructing operation is performed by an amount allowed within the idle time, thereby re-creating the data. The time required for the construction operation can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration of a conventional disk array device.
FIG. 2 is a schematic diagram for explaining a parity generation operation.
FIG. 3 is a schematic diagram illustrating an operation of restoring original data using parity.
FIG. 4 is a block diagram showing an embodiment of a data recording / reproducing apparatus according to the present invention.
FIG. 5 is a schematic diagram illustrating a data format of serial transfer according to an embodiment of the present invention.
FIG. 6 is a block diagram showing a configuration example of a disk array device used in one embodiment of the present invention.
FIG. 7 is a timing chart showing an operation example of one embodiment of the present invention.
FIG. 8 is a timing chart showing a first example of a data reconstructing operation in one embodiment of the present invention.
FIG. 9 is a timing chart showing a second example of the data reconstructing operation in one embodiment of the present invention.
FIG. 10 is a timing chart showing a third example of the data reconstructing operation in one embodiment of the present invention.
[Explanation of symbols]
9 CPU, 16 Data multiplexer, 17 Parity operation circuit, 18-22 Memory controller, 38-43 Disk array device, 58, 59 Video data controller

Claims (2)

In a data recording / reproducing apparatus adapted to record data in units of time slots on a plurality of non-linearly accessible recording media,
A recording and reproducing unit for recording and reproducing the data on and from the plurality of recording media,
A system management controller arranged at a predetermined interval and using a system management time slot in which a command for management is arranged from a higher order,
When it is detected that the data recorded on any of the plurality of recording media cannot be reproduced,
Controlling the recording and reproducing unit to reproduce the data and the error correction data from the reproducible recording medium, in the system management time slot where it is detected that there is no command for the management, A data recording / reproducing apparatus comprising: a control unit configured to reconstruct the unreproducible data from the reproducible data from the recording medium and the error correction data. In a data recording / reproducing method adapted to record data in units of time slots on a plurality of non-linearly accessible recording media,
By a recording and reproducing unit, the data is recorded and reproduced on the plurality of recording media,
The system management controller uses system management time slots that are arranged at predetermined intervals and in which commands for management are arranged from the upper level,
When it is detected that the data recorded on any of the plurality of recording media cannot be reproduced,
Controlling the recording and reproducing unit to reproduce the data and the error correction data from the reproducible recording medium, in the system management time slot where it is detected that there is no command for the management, A data recording / reproducing method, comprising reconstructing the unreproducible data from the reproducible data from the recording medium and the error correction data.

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