Abstract: Methods and apparatus for accessing a redundant array of independent drives (RAID) storage device are disclosed. In some embodiments file data is broken into multiple segments. A cryptographic operation is performed on one or more segments to generate encrypted segment(s). One or more parity syndrome is computed from the encrypted segment(s) and the unencrypted segment(s). The encrypted segment(s), the unencrypted segment(s) and the parity syndrome(s) are striped onto different individual drives. Since the cryptographic operation is not performed on all the segments, it may also be performed concurrently with computing of parity syndrome(s) from other unencrypted segments.

Abstract: When parity checking in a disk array such as a RAID-6 system determines data and parity information is unsynchronized, additional calculations are performed to determine whether the error may be attributed to faulty data on a disk drive or to a more systemic problem such as a faulty controller. In particular, for each particular error detected, the parity generating information is analyzed to determine if each error involves a common disk index. If so, the data can be corrected on that disk; if not other corrective procedures are implemented.

Abstract: A system and method of utilizing a network to correct flawed media data. The media device includes a processor, a memory, a network adapter, a removable media interface, an error-correction module, and a communication module. The network device enables the media device to connect to the network and server. The removable media interface enables a user to couple a removable medium to the media device. After a user inserts a removable medium into the removable media interface, the processor and error-correction module examines the removable medium for physical errors. If the number of detected errors exceeds a predetermined threshold, the media device, via the network adapter and the communication module, queries a server for correction data. This correction data may be utilized by the media device to enable successful processing of the data stored on the removable medium.

Abstract: A triple parity (TP) technique reduces overhead of computing diagonal and anti-diagonal parity for a storage array adapted to enable efficient recovery from the concurrent failure of three storage devices in the array. The diagonal parity is computed along diagonal parity sets that collectively span all data disks and a row parity disk of the array. The parity for all of the diagonal parity sets except one is stored on the diagonal parity disk. Similarly, the anti-diagonal parity is computed along anti-diagonal parity sets that collectively span all data disks and a row parity disk of the array. The parity for all of the anti-diagonal parity sets except one is stored on the anti-diagonal parity disk. The TP technique provides a uniform stripe depth and an optimal amount of parity information.

Abstract: An apparatus and method for recording and/or reproducing data on a disc are provided using padding information, and a corresponding information storage medium. The recording method includes recording a recording unit block in which invalid data is padded in part of the block and recording padding information indicating that the invalid data is included. According to the method, a disc drive becomes able to distinguish valid data from invalid data in an error correction block such that reliability of reproduction increases and stability of the system is improved.

Abstract: A method for auto-correction of errors in an array of solid-state storage devices having a plurality of storage channels dedicated to storing parity data to provide fault tolerance for a loss of at least two of the plurality of storage channels. A read operation from the storage channels transfers data to a plurality of channel memories. The data in the channel memories is checked to confirm the data is valid. Responsive to detection of invalid data, the data may be tested to identify the storage channel in error, including sequentially excluding data read form a different one of the plurality of channel memories from a parity check and determining the validity of data from remaining channel memories. If valid data is obtained, the storage channel from which the data was excluded is identified as the storage channel in error.

Abstract: Several methods and apparatus to single XOR operation weaver reconstruction of a failed drive of a raid are disclosed. A failed drive of the drive group implemented in a WEAVER code with an (n,t,t) layout is determined. A set of scatter/gather lists is produced from a number of the other drives of the drive group. A scatter/gather list is created by modifying a pointer data of the set of scatter/gather lists. An additional scatter/gather list is generated from the set of scatter/gather lists. A single XOR operation is performed on the data segment, the parity segment, the additional data segment and the additional parity segment to form a resulting scatter/gather list including a resulting data segment and a resulting parity segment. The resulting data segment and the resulting parity segment are written as sequenced in the resulting scatter/gather list to a replacement drive.

Abstract: Implementations described herein generally provide methods, systems and media for recovering data from disk failures. One method generally includes calculating a global parity for a group of disks comprising multiple independent RAID (Redundant Array of Independent Disks) arrays; determining if a two disk failure has occurred within a single RAID array; and if so, recovering from the two disk failure using the global parity and data from the RAID arrays.

Abstract: A Redundant Array of Inexpensive Disks (RAID) controller comprises a RAID error correction code (ECC) encoder module that receives data for storage and that generates code words for data drives and one or more parity drives, which have physical locations. The code words are generated based on the data and a cyclic code generator polynomial. Logical locations correspond to index positions in the cyclic code generator polynomial. A mapping module maps the physical locations of the data and parity drives to the logical locations. The mapping module adds a new data drive to an unused one of the logical locations. A difference generating module generates a difference code word based on the new data drive. The RAID ECC encoder module encodes the difference code word and adds the encoded difference code word to an original code word generated before the new data drive is added.

Abstract: A method begins by a first device obtaining data for transmission to a second device and partitioning the data to produce a plurality of data portions. The method continues with the first device dispersed storage error encoding the plurality of data portions using a plurality of sets of error coding dispersal storage function parameters to produce a plurality of sets of encoded data slices and transmitting the plurality of sets of encoded data slices to the second device via a network. The method continues with a second device receiving at least a decode threshold number of encoded data slices and dispersed storage error decoding the at least a decode threshold number of encoded data slices to produce a decoded data portion for each set of the plurality of sets of encoded data slices. The method continues with the second device recapturing the data from a plurality of decoded data portions.

Abstract: A method and system for syndrome generation and data recovery is described. The system includes a parity generator coupled to one or more storage devices to generate parity for data recovery. The parity generator includes a first comparator to generate a first parity factor based on data in one or more of the storage devices, a multiplier to multiply data from one or more of the storage devices with a multiplication factor to generate a product, a second comparator coupled to the multiplier to generate a second parity factor based at least in part on the product, and a selector to choose between the first parity factor and the second parity factor.

Abstract: A method of storing data is disclosed. A set of data blocks, including a plurality of proper subsets of data blocks, is stored. A plurality of first-level parity blocks is generated, wherein each first-level parity block is generated from a corresponding proper subset of data blocks within the plurality of proper subsets of data blocks without reference to other data blocks not in the corresponding proper subset. A second-level parity block is generated, wherein the second level parity block is generated from a plurality of data blocks included in at least two of the plurality of proper subsets of data blocks, and wherein recovery of a lost block in a given proper subset of data blocks is possible without reference to any data blocks not in the given proper subset.

Abstract: A system and method are provided for efficiently initializing a redundant array of independent disks (RAID). The method monitors host write operations and uses that information to select the optimal method to perform a parity reconstruction operation. The bins to which data access write operations have not occurred can be initialized using a zeroing process. In one aspect, the method identifies drives in the RAID array capable of receiving a ‘WriteRepeatedly’ command and leverages that capability to eliminate the need for the RAID disk array controller to provide initialization data for all disk array initialization transfers. This reduces the RAID array controller processor and I/O bandwidth required to initialize the array and further reduces the time to initialize a RAID array. In a different aspect, a method is provided for efficiently selecting a host write process for optimal data redundancy and performance in a RAID array.

Abstract: Various embodiments of the present invention provide fault-tolerant, redundancy-based data-storage systems that rely on disk-controller-implemented error detection and error correction, at the disk-block level, and RAID-controller-implemented data-redundancy methods, at the disk and disk-stripe level, in order to provide comprehensive, efficient, and system-wide error detection and error correction. Embodiments of the present invention use disk-level and stripe-level data redundancy to provide error detection and error correction for stored data objects, obviating the need for certain costly, intermediate levels of error detection and error correction commonly employed in currently available fault-tolerant, redundancy-based data-storage systems.

Abstract: An apparatus and method for recording and/or reproducing data on a disc are provided using padding information, and a corresponding information storage medium. The recording method includes recording a recording unit block in which invalid data is padded in part of the block and recording padding information indicating that the invalid data is included. According to the method, a disc drive becomes able to distinguish valid data from invalid data in an error correction block such that reliability of reproduction increases and stability of the system is improved.

Abstract: A method for determining a fault tolerance of an erasure code includes deriving base erasure patterns from a generator matrix of an erasure code, determining which of the base erasure patterns are adjacent to one another and XORing the adjacent base erasure patterns with one another to produce child erasure patterns of the erasure code. The method further includes combining the base erasure patterns and the child erasure patterns to form a minimal erasures list (MEL) for the erasure code, whereby the MEL corresponds to the fault tolerance of the erasure code. Also provided are methods for communicating and storing data by using the fault tolerance of erasure codes.

Abstract: A data structure for a flash memory and data reading/writing method thereof are disclosed. A 512 bytes data and a redundant code derived from the data encoded with a 6-bit error correcting code scheme are stored in a first sector and a second sector with sequential address in a block of the flash memory respectively. A logic block address information of this block is divided into two parts that are stored in the first sector and the second sector respectively.

Abstract: A data recorder includes a first memory element including read/write capability, a second memory element including non-volatile memory and a controller for realizing memory management functions. The controller responds to a predetermined triggering event by writing selected data from the first memory element to the second memory element. The selected data include data units that have been modified after a prior triggering event.

Abstract: Error correction and detection in a redundant memory system that includes a memory controller; a plurality of memory channels in communication with the memory controller, the memory channels including a plurality of memory devices; a cyclical redundancy code (CRC) mechanism for detecting that one of the memory channels has failed, and for marking the memory channel as a failing memory channel; and an error correction code (ECC) mechanism. The ECC is configured for ignoring the marked memory channel and for detecting and correcting additional memory device failures on memory devices located on one or more of the other memory channels, thereby allowing the memory system to continue to run unimpaired in the presence of the memory channel failure.

Abstract: Described herein are method and apparatus for storing data to a low-latency random read memory (LLRRM) device using non-aligned data striping, the LLRRM device being implemented on a storage system. The LLRRM device may comprise a bank comprising a plurality of memory chips, each chip being simultaneously accessible for storing data on a plurality of erase-units (EUs). A storage operating system may maintain, for each chip, a reserve data structure listing reserve EUs and a remapping data structure for tracking remappings between defective EUs to reserve EUs in the chip. A defective EU in a chip may be mapped to a reserve EU from the reserve data structure. Upon receiving a data block to be stored to the LLRRM device at the defective EU, the storage operating system may stripe the received data block across a plurality of chips in a non-aligned manner using the remapped reserve EU.

Abstract: An efficient method to apply an erasure encoding and decoding scheme across dispersed data stores that receive constant updates. A data store is a persistent memory for storing a data block. Such data stores include, without limitation, a group of disks, a group of disk arrays, or the like. An encoding process applies a sequencing method to assign a sequence number to each data and checksum block as they are modified and updated onto their data stores. The method preferably uses the sequence number to identify data set consistency. The sequencing method allows for self-healing of each individual data store, and it maintains data consistency and correctness within a data block and among a group of data blocks. The inventive technique can be applied on many forms of distributed persistent data stores to provide failure resiliency and to maintain data consistency and correctness.

Abstract: An XOR circuit, a RAID device which can recover several failures and method thereof are provided. A Galois field data recovery circuit having two or more sets of Galois Field engine circuits which are used in the XOR circuit, is one which can generate high efficient parity engine and high efficient flow data route and which at the same time correct the three or more failures during operation of the RAID device.

Abstract: To suppress deterioration in image quality even if skew occurs during conveyance of a medium, an apparatus, which is configured to record on the medium conveyed in a direction that intersects an array direction of a plurality of recording elements using a recording head on which the recording elements are arranged, includes a table in which the recording elements are divided into a plurality of groups, and which includes correction information corresponding to the recording elements for each group, a first acquisition unit configured to acquire position information about the medium in the array direction, a second acquisition unit configured to acquire the correction information based on the position information and the table, and a correction unit configured to correct image data based on the correction information.

Abstract: A RAID disk drive controller (FIG. 33) implements disk storage operations, including striping and redundancy operations with multiple disk drives connected via respective SATA ports (520). Configurable data path switch logic (460) provides dynamic configuration of two or more attached drives into one or more arrays. Data transfers are synchronized locally by leveraging the SATA port transport layer FIFO (530). Synchronous transfers allow on-the-fly redundancy (XOR) operations (FIG. 36) for improved performance and reduced hardware complexity. XOR accumulator hardware (FIG. 42-FIG. 43) reduces buffer requirements for multiple DMA channels otherwise required for synchronization, and various narrow and wide striping modes are supported.

Abstract: A digital broadcasting system which is robust against an error when mobile service data is transmitted and a method of processing data are disclosed. The mobile service data is subjected to an additional coding process and the coded mobile service data is transmitted. Accordingly, it is possible to cope with a serious channel variation while applying robustness to the mobile service data.

Abstract: A disk array apparatus, if a rebuild error occurs, stores information indicating an error occurrence place in a sector holding unit, and then stops rebuild processing. A host computer, if a rebuild error occurs in the disk array apparatus, acquires the information indicating the error occurrence place from the disk array apparatus. The host computer determines whether the rebuild error does not obstruct continuation of the rebuild processing based on the acquired information indicating the error occurrence place. If it is determined that the rebuild error does not obstruct continuation of the rebuild processing, the host computer instructs the disk array apparatus to resume the rebuild processing while skipping the error occurrence place. In response to the instruction from the host computer, the disk array apparatus resumes the rebuild processing while skipping the error occurrence place.

Abstract: According to one embodiment, a data storage apparatus including memory chips includes an error correction encoder, a RAID controller, error detectors and memory units. Each of the memory chips includes a semiconductor memory. The error correction encoder adds an error correction code to an encoded data stream. The RAID controller divides the encoded data stream from the error correction encoder into data blocks. The RAID controller generates a parity data block based on the data blocks. The RAID controller outputs the data blocks and parity data block to the error detectors, respectively. The error detectors add an error detection code to the data blocks and parity data block output from the RAID controller. Each of the memory units includes the memory chips. The memory units write the data blocks and parity data block from the error detectors to the memory chips.

Abstract: Embodiments of the invention provide methods and systems for improving the reliability of data stored on disk media. Logical redundancy is introduced into the data, and the data within a logical storage unit is divided into sectors that are spatially separated by interleaving them with sectors of other logical storage units. The logical redundancy and spatial separation reduce or minimize the effects of localized damage to the storage disk, such as the damage caused by a scratch or fingerprint. Thus, the data is stored on the disk in a layout that improves the likelihood that the data can be recovered despite the presence of an error that prevents one sector from being read correctly.

Abstract: A method for auto-correction of errors in an array of disk storage devices having a plurality of disk storage devices dedicated to storing parity data to provide fault tolerance for a loss of at least two of the plurality of disk storage devices. A read operation from the storage channels transfers data to a plurality of disk channel memories. The data in the disk channel memories is checked to confirm the data is valid. Responsive to detection of invalid data, the data may be tested to identify the disk storage channel in error, including sequentially excluding data read from a different one of the plurality of disk channel memories from a parity check and determining the validity of data from remaining disk channel memories. If valid data is obtained, the disk storage channel from which the data was excluded is identified as the disk storage channel in error.

Abstract: A system and related method for calculating parity information for disk array drive failure recovery. More specifically, using eight bit coefficients and calculating parity information using valid eight bit encryption keys to produce finite field encrypted resultant multiplication. Further disclosed is a method of determining whether a potential encryption key of a particular number of bits produces valid results for all possible multiplications in determining parity values.

Abstract: A triple parity (TP) technique reduces overhead of computing diagonal and anti-diagonal parity for a storage array adapted to enable efficient recovery from the concurrent failure of three storage devices in the array. The diagonal parity is computed along diagonal parity sets that collectively span all data disks and a row parity disk of the array. The parity for all of the diagonal parity sets except one is stored on the diagonal parity disk. Similarly, the anti-diagonal parity is computed along anti-diagonal parity sets that collectively span all data disks and a row parity disk of the array. The parity for all of the anti-diagonal parity sets except one is stored on the anti-diagonal parity disk. The TP technique provides a uniform stripe depth and an optimal amount of parity information.

Abstract: A method for recovering from three failed data storage devices is disclosed. A plurality of data storage devices hold data, and a row parity storage device holds row parity for them. The data storage devices and the row parity storage device form a set of storage devices. A diagonal parity storage device and an anti-diagonal parity storage device hold parity computed diagonally over the set of storage devices. In the event of a failure of three data storage devices of the set of storage devices, a first failed storage device is chosen for first restoration. A missing block of the first failed storage device is computed by using the remaining set of storage devices, and the diagonal parity storage device, and the anti-diagonal parity storage device. The remaining two failed storage devices are restored by a diagonal parity restoration technique.

Abstract: Provided are a method, system, and article of manufacture, wherein a determination is made that a first data array in a plurality of data arrays has to be repaired to replace a failed storage device within the first data array. A storage device is selected from a selected data array of the plurality of data arrays to replace the failed storage device, wherein a data value corresponding to the selected data array is less than the data value corresponding to the first data array.

Abstract: Disclosed is an apparatus for recovering data in the case of single or double failures of N partial data blocks generated by dividing the data where N is a natural number greater than 1. The apparatus recovers the data on the basis of a Galois field product computation table including first and second search key data, and products of the first and second search key data. The first search key data includes possible symbol values. The second search key data includes a weighting value set and an inversed weighting value set. The weighting value set includes weighting values each assigned to one of the N partial data blocks and different from each other, and is closed under addition in the Galois field. The inversed weighting value set includes multiplicative inverses of the weighting values included in the weighting value set.

Abstract: A symmetric triple parity (TP) technique in an array comprising a number p of storage devices, such as disks, with p being a prime number is provided. The p disks are organized as one row parity disk, two symmetric parity disks and p-3 data disks. Phantom diagonal and anti-diagonal parity disks assumed to be present are further assumed to contain a predetermined value, thereby enabling parity encoding/decoding utilizing the phantom (anti-) diagonal disks. Row parity and symmetric parity values are included within the computation of the diagonal and anti-diagonal parities; accordingly, the two symmetric parity and the row parity values may be computed using the same technique as used for a triple parity erasure, i.e., in a symmetric fashion.

Abstract: A method for encoding a block of data to allow it to be stored or transmitted correctly in the face of accidental or deliberate modifications, the method including constructing a number n greater than one of original components, each of which is derived from the block and each of which is smaller than the block, and combining original components to construct a number m greater than one of new components, wherein each of the new components is smaller than the sum of the sizes of the original components combined to produce it, wherein the block can be reconstructed from any set of n different components selected from the original components and new components, and wherein a set of n different components selected from the original components and new components contains more redundant information about the block than the set of n original components.

Abstract: A rotating parity redundant array of independent disk (RAID) and a method for storing parity of the same are provided. The rotating parity RAID comprises a first˜a third disk. The first disk has A1˜Am blocks for storing A1˜Am data respectively. The second disk has B1˜Bm blocks for storing B1˜Bm data respectively. The third disk has C1˜Cm blocks for storing C1˜Cm data respectively. The Cn+k data is an nth parity data obtained from the An data and the Bn data. The Bn+k+1 data is an (n+1)th parity data obtained from the Cn+1 data and the An+1 data. The An+k+2 data is an (n+2)th parity data obtained from the Bn+2 data and the Cn+2 data.

Abstract: An apparatus, system, and method are disclosed for hard disk drive redundancy. A demarcation module demarks a parity data block in each set of a specified number of data blocks on a hard disk drive. An association module associates a PBA of each un-demarked data block with a LBA. A write module writes the data to the un-demarked data blocks. A parity module calculates parity data for the data written to the un-demarked data blocks and the write module writes the parity data to the parity data block.

Abstract: Systems and methods are provided for disabling an array port in an enterprise storage system. In one embodiment, a system comprises a storage area network (SAN), a plurality of hosts, an array controller comprising a plurality of array ports, and a management server. The management server receives a request to disable an identified one of the plurality of array ports and identifies, from a configuration table stored in the management system server, one or more of the plurality of hosts having at least one path to the identified array port. The management server transmits an instruction to the one or more of the plurality of hosts to disable paths to the identified array port.

Abstract: Non volatile storage may be employed to temporarily store data which is destaged to data storage drives. The non volatile storage is configured to preserve the data through a power outage. Some data may be preserved, but is not needed, such as the result of a failover to another non volatile storage. This unneeded data is tested to verify the non volatile storage by indicating whether the data survived the power cycle from full power to self refresh mode battery power to full power, without risking the loss of data that is needed.

Abstract: A storage system comprises a first storage device having a first plurality of hard disk drives and a first controller. The first controller stores data in the first plurality of hard disk drives by stripes. Each stripe includes M data and N parity data allocated to M+N hard disk drives of the first plurality of hard disk drives. A first hard disk drive includes data or parity data of both a first stripe of the stripes and a second stripe of the stripes, while a second hard disk drive includes data or parity data of only one of the first stripe or the second stripe. During data recovery involving failure of one of the first plurality of hard disk drives, the data in the failed hard disk drive is recovered for each stripe by calculation using data and parity data in other hard disk drives for each stripe.

Abstract: A stream including plural access units is recorded on an information recording medium. Each access unit has a first packet that includes basic data as well as a second packet which includes extension data related to the basic data. The basic data is data that is decodable in a completed state without using extension data, and the extension data is data for improving the quality of data generated from the basic data. The header of the first packet holds first information, which indicates that the first packet includes the basic data, and the header of the second packet holds second information which indicates that the second packet includes the extension data. This arrangement allows a decoder that decodes only basic data to process the access unit, which includes the basic data and the extension data.

Abstract: Embodiments in accordance with the present invention help a disk drive to effectively cope with a data address mark detection error. In one embodiment, a data sector is provided with plural data address marks and an read/write (RW) channel reads out the data sector using part of those data address marks. Each divisional section of a split sector has two data address marks and the RW channel uses one of the two data address marks. A data address mark to be used is specified by a register. When an error occurs in detecting a data address mark, its position is stored in a register. Based on the error position, an error recovery processing section stores, in the register, a data address mark to be used in a next retry.

Abstract: A RAID 6 system, which has two strips to hold redundant data, employs a memory array controller that at each “read” operation considers not just the data but also the redundant information, even in the absence of any indication from the collection of memory controllers associated with the hard drives that any error condition exists. Thus, with each “read” operation the array controller checks the data for an unreported error, and takes corrective action when an error condition is discovered.

Abstract: In one embodiment, the present invention includes a method for determining from a data block in a buffer a number of first operands in a first portion of the buffer and a number of second operands in a second portion of the buffer. Based on these numbers, a cyclic redundancy checksum (CRC) operation may be iteratively performed on the first and second operands to obtain a checksum result. The first and second operands are of a different length, and the checksum operation may be executed using processor instructions corresponding to the different lengths. Other embodiments are described and claimed.

Abstract: A complementary error evaluator polynomial is generated by obtaining a syndrome polynomial and one or more erasure locations. The syndrome polynomial and the erasure locations are associated with Reed-Solomon encoded information. A complementary error evaluator polynomial and an error locator polynomial are simultaneously generated using the syndrome polynomial and the erasure locations where the complementary error evaluator polynomial is a complement of the error evaluator polynomial.

Abstract: The present disclosure includes methods and devices for stripe-based memory operation. One method embodiment includes writing data in a first stripe across a storage volume of a plurality of memory devices. A portion of the first stripe is updated by writing updated data in a portion of a second stripe across the storage volume of the plurality of memory devices. The portion of the first stripe is invalidated. The invalid portion of the first stripe and a remainder of the first stripe are maintained until the first stripe is reclaimed. Other methods and devices are also disclosed.

Abstract: A RAID disk drive controller (FIG. 33) implements disk storage operations, including striping and redundancy operations with multiple disk drives connected via respective SATA ports (520). Configurable data path switch logic (460) provides dynamic configuration of two or more attached drives into one or more arrays. Data transfers are synchronized locally by leveraging the SATA port transport layer FIFO (530). Synchronous transfers allow on-the-fly redundancy (XOR) operations (FIG. 36) for improved performance and reduced hardware complexity. XOR accumulator hardware (FIG. 42-FIG. 43) reduces buffer requirements for multiple DMA channels otherwise required for synchronization, and various narrow and wide striping modes are supported.

Abstract: Optical discs are adapted to be used with a light beam having a wavelength of 405 nm for recording or reproducing data. Error correcting blocks for recording BMID including copy protection key information are defined on optical discs (1) dedicated to data reproduction. A data string of BMID to be recorded has 64 bytes. An error correcting block is constituted by 304 columns of error correcting code words (LDC). A BMID data string of 64 bytes is inserted to predetermined 64 error correcting code words (LDC) of a block (304 columns of error correcting code words). The total code length of the predetermined 64 error correcting code words (LDC) is 248 bytes, of which a predetermined byte (symbol) is replaced by a predetermined byte (symbol) of the BMID data string.

Abstract: A data storage apparatus using a plurality of hard disk drives for storing stream data includes a command receiving portion for receiving a stream data read command from the outside; and a data processing portion reading the stream data stored in the hard disk drives upon receiving the read command, assembling the data, and transferring the assembled stream data to the outside. The apparatus further includes a control portion performing control of determining maximum time from receiving the read command to completing the assembly of the stream data, terminating the data read from the hard disk drives in the case where the maxim time has elapsed, and preparing the stream data transferred to the outside in the data processing portion only using data having been read; and a managing portion variably setting the maximum time according to a bit rate of the stream data read on the read command.