Disk array system

• US 7,453,774 B2
• Filed: 12/30/2004
• Issued: 11/18/2008
• Est. Priority Date: 11/28/2003
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ogawa, Takuji, Yagisawa, Ikuya, Kano, Azuma
• Primary Examiner(s): Neyzari; Ali
• Application Number:
  US11/024,626
• Publication Number:
  US 20050120263A1
• Time in Patent Office: 1,419 Days
• Field of Search: 369/30.28, 369/30.38, 369/30.58, 369/30.29, 369/30.06, 369/30.04, 369/30.41, 369/30.46, 369/30.43, 369/34.01, 714/6.111, 714/43, 714/112, 711/114
• US Class Current: 369/30.28
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 3/0614 Improving the reliability of storage systems
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: G11B 20/18 Error detection or correction; Testing , e.g. of drop-outs

Abstract

A disk array system having first and second housings and a controller for controlling the first and second housings. Fiber channel hard disk drives are received in the first housing, and serial ATA hard disk drives are received in the second housing. When reading data stored in a serial ATA hard disk drive in the second housing, the controller reads a plurality of pieces of data including the data to be read and parity data for the plurality of pieces of data from all the hard disk drives of an RAID group to which the hard disk drive storing the data to be read belongs. Thus, the controller examines whether the plurality of pieces of data including the data to be read are written in the hard disk drives with erroneous contents or not.

Claims

1. A disk array system connectable with an information processing device, said disk array system comprising:

first and second disk controllers each adapted to be coupled to said information processing device to so as to control transfer of data received from the coupled information processing device;

an expansion housing installed with a first set of disk drive units each adapted to be coupled to said first and second disk controllers when installed in said disk array system,

wherein each of said disk drive units comprises a converter and a disk drive, said disk drive provided with an interface accessible in accordance with a Serial ATA protocol, said converter executing conversion of protocols for transmitting data between a Fibre Channel protocol and the Serial ATA protocol, said disk drive receiving data via said converter and storing the received data.

2. A disk array system according to claim 1,

wherein said expansion housing further comprises a plurality of power supply modules adapted to control supply of power to said disk drive units,

wherein both of said first and second disk controllers are provided outside of said expansion housing.

3. A disk array system according to claim 1, wherein said converter in each of said disk drive units is coupled to both said first disk controller and said second disk controller.

4. A disk array system according to claim 1, further comprising:

another housing comprising said first disk controller and said second disk controller;

wherein said expansion housing comprises a plurality of port bypass circuits, one of said port bypass circuits is coupled to said converter in at least one of said disk drive units.

5. A disk array system according to claim 1,

wherein said expansion housing comprises a first port bypass circuit coupled to said first disk controller and a second port bypass circuit coupled to said second disk controller,

wherein said converter in one of said disk drive units is coupled to both said first port bypass circuit and said second port bypass circuit.

6. A disk array system according to claim 1, wherein said expansion housing comprises a circuit board, said circuit board comprising a plurality of port bypass circuits and being coupled to said converter of each of said disk drive units.

7. A disk array system according to claim 1, further comprising:

a first computer program stored on a computer readable storage medium and implemented in said first disk controller, the first computer program comprising;

code controlling two or more of said disk drive units to form a first Redundant Array of Inexpensive Disks (RAID) group; and

code arranged to form at least one first logical volume related to said first RAID group, said first logical volume being a logical area to be stored data transferred from said information processing device; and

a second computer program stored on a computer readable storage medium and implemented in said second disk controller, the second computer program comprising;

code controlling two or more said disk drive units to form a second RAID group by using; and

code arranged to form at least one second logical volume related to said second RAID group, said second logical volume being a logical area to be stored data transferred from said information processing device.

8. A disk array system according to claim 1, further comprising:

another housing;

a second set of disk drive units provided in said another housing, each of said second set of disk drive units comprising a disk drive provided with an interface accessible in accordance with the Fibre Channel protocol; and

a plurality of second power supply modules provided in said another housing and arranged so as to control supply of power to said second set of disk drive units.

9. A disk array system according to claim 1, further comprising:

a second set of disk drive units each comprising a disk drive provided with an interface accessible in accordance with the Fibre Channel protocol,

wherein said first disk controller is arranged to control transfer of data from/to said disk drive in each of said first set of disk drive units as well as in each of said second set of disk drive units.

10. A disk array system according to claim 1, further comprising:

a first communication medium, said first disk controller being arranged to control the transfer of data via said first communication medium; and

a second communication medium, said second disk controller being arranged to control the transfer of via said second communication medium;

wherein each of said disk drive units comprises a first port coupled to said first communication medium and a second port coupled to said second communication medium.

11. A disk array system according to claim 1,

wherein said first disk controller controls transfer of data from/to said disk drive units via a first Fibre Channel-Arbitrated Loop;

wherein said second disk controller controls transfer of data from/to said disk drive units via a second Fibre Channel-Arbitrated Loop; and

wherein each of said disk drive units comprises a first port coupled to said first Fibre Channel-Arbitrated Loop and a second port coupled to said second Fibre Channel-Arbitrated Loop.

12. A disk array system according to claim 1, further comprising:

a first computer program stored on a computer readable storage medium and implemented in said first disk controller with code controlling two or more of said disk drive units to form a first Redundant Array of Inexpensive Disks (RAID) group; and

a second computer program stored on a computer readable storage medium and implemented in said second disk controller with code controlling two or more of said disk drive units to form a second RAID group.

13. A disk array system according to claim 1, further comprising:

a first computer program stored on a computer readable storage medium and implemented in said first disk controller with code arranged to form a first logical volume, said first logical volume being adapted to stored data transferred with a first Logical Unit Number from said information processing device; and

a second computer program stored on a computer readable storage medium and implemented in said second disk controller with code arranged to form a second logical volume, said second logical volume being adapted to store data transferred with a second Logical Unit Number from said information processing device.

14. A disk array system according to claim 1, wherein each of said disk drive units is removably inserted in said expansion housing.

15. A disk array system connectable with a host computer, said disk array system comprising:

a first disk controller comprising a first cache memory and controlling transfer of data received from said host computer to write received data to said first cache memory;

a second disk controller comprising a second cache memory and controlling transfer of data received from said host computer to write received data to said second cache memory; and

an expansion housing comprising a first set of disk drive units each provided with a converter and a disk drive having an interface which transfers data in accordance with the Serial ATA protocol, said converter coupled to said first and second disk controllers and converting protocols for transmitting data between a Fibre Channel protocol and a Serial ATA protocol,

wherein, when one of said first and second disk controllers transmits data to one of the disk drive units in accordance with the Fibre Channel protocol, the data is converted to the Serial ATA protocol by said converter and the converted data is transferred to said one of the disk drive units for storing received data.

16. A disk array system according to claim 15,

wherein said expansion housing further comprises at least one supply module arranged to control supply of power to said disk drive units,

wherein both of said first and second disk controllers are provided outside of said expansion housing.

17. A disk array system according to claim 15,

wherein said converter is coupled to both of first and second communication mediums,

wherein said first communication medium is arranged to relay data according to the Fibre Channel protocol between said first disk controller and one of said disk drive units,

wherein said second communication medium is arranged to relay data according to the Fibre Channel protocol between said second disk controller and one of said disk drive units.

18. A disk array system according to claim 17, wherein said expansion housing further comprises a plurality of port bypass circuits coupled to the corresponding converter means.

19. A disk array system according to claim 15,

wherein said expansion housing comprises a first port bypass circuit coupled to said first disk controller and a second port bypass circuit coupled to said second disk controller,

wherein said converter is coupled to both of said first port bypass circuit and said second port bypass circuit.

20. A disk array system according to claim 15, further comprising another housing and a plurality of port bypass circuits coupled to said converter,

wherein said first and second disk controllers are disposed in said another housing, wherein said expansion housing is provided with said plurality of port bypass circuits.

21. A disk array system according to claim 15, further comprising:

a first computer program stored on a computer readable storage medium and implemented in the first disk controller, the first computer program comprising;

code arranged so that the first computer program when executed with the code controls two or more of said disk drive units to form a first Redundant Array of Inexpensive Disks (RAID) group; and

code arranged so that the first computer program when executed with the code controls to form at least one first logical volume related to said first RAID group, said first logical volume being a logical area to be stored data transferred from said host computer; and

a second computer program stored on a computer readable storage medium and implemented in the second disk controller, the second computer program comprising;

code arranged so that the second computer program when executed with the code controls two or more of said disk drive units to form a second RAID group; and

code arranged so that the second computer program when executed with the code controls to form at least one second logical volume related to said second RAID group, said second logical volume being a logical area to be stored data transferred from said host computer.

22. A disk array system according to claim 15, further comprising:

a second set of disk drive units each comprising a disk drive formed with an interface which transfers data in accordance with a Fibre Channel protocol, said second set of the disk drive units excluding one formed with an interface which transfers data in accordance with a Serial ATA protocol; and

another housing installed with said second set of the disk drive units and a plurality of power supply modules, each of said power supply modules controlling to supply power to said second set of the disk drive units.

23. A disk array system according to claim 15, further comprising:

a second set of disk drive units each comprising a disk drive formed with an interface which transfers data in accordance with a Fibre Channel protocol;

wherein said first disk controller controls transfer of data to the disk drive in each of said first set of the disk drive units as well as the disk drive in each of said second set of the disk drive units.

24. A disk array system according to claim 15, further comprising first and second communication mediums each transmitting data in accordance with a Fibre Channel-Arbitrated Loop,

wherein said first disk controller controls transfer of data to the disk drive in each of said disk drive units via said first communication medium in accordance with the Fibre Channel-Arbitrated Loop

wherein said second disk controller controls transfer of data to the disk drive in each of said disk drive units via said second communication medium in accordance with the Fibre Channel-Arbitrated Loop.

25. A disk array system according to claim 15, further comprising:

a first computer program stored on a computer readable storage medium, implemented in said first disk controller and arranged to control two or more of said disk drive units to form a first Redundant Array of Inexpensive Disks (RAID) group; and

a second computer program stored on a computer readable storage medium, implemented in said second disk controller, and arranged to control two or more of said disk drive units to form a second RAID group.

26. A disk array system according to claim 15, further comprising:

a first computer program stored on a computer readable storage medium, implemented in said first disk controller, and arranged to form a first logical volume adapted to store data transferred with a first Logical Unit Number from said host computer; and

a second computer program stored on a computer readable storage medium, implemented in said second disk controller, and arranged to form a second logical volume adapted to store data transferred with a second Logical Unit Number from said host computer.

27. A disk array system according to claim 15, wherein each of said disk drive units is removably inserted in said expansion housing.

28. A disk array system connectable with an information processing device, said disk array system comprising:

first and second controllers controlling transfer of data received from said information processing device according to a Fibre Channel protocol;

first and second Fibre-Channel-Arbitrated Loops (FC-ALs); and

an expansion housing installed with a first set of disk drive units each provided with a disk drive and a converter which receives data sent from said first controller and/or said second controller according to the Fibre Channel protocol and sends data to said disk drive according to a Serial ATA protocol, said disk drive receiving data according to the Serial ATA protocol,

wherein said converter of each of said first set of disk drive units is coupled to said first controller via a first circuit of said first FC-AL, as well as to said second controller via a second circuit of said second FCA-AL, and

wherein each of said first circuit of said first FC-AL and said second curcuit of said second FC-AL comprises a function of bypassing a failed disk drive.

29. A disk array system according to claim 28, wherein said expansion housing comprises a plurality of power supply modules, each of said power supply modules controlling to supply power to said first set of disk drive units.

30. A disk array system according to claim 28, further comprising:

a first port being connected to said first circuit of said first FC-AL to relay data between said second controller and said first set of disk drive units,

a second port being connected to said second circuit of said second FC-AL to relay data between said first controller and said first set of disk drive units.

31. A disk array system according to claim 28,further comprising another housing,

wherein said first and second controllers are disposed in said another housing,

wherein said expansion housing is provided with said first and second circuits.

32. A disk array system according to claim 28, wherein said expansion housing comprises said first and second circuits, each of said first and second circuits being a port bypass circuit.

33. A disk array system according to claim 28, wherein said expansion housing comprises a circuit board, said circuit board comprising said first and second circuits.

34. A disk array system according to claim 28, further comprising:

a first computer program stored on a computer readable storage medium and implemented in said first controller, said first computer program, when executed, controlling two or more disk drives of said first set of disk drive units to form a first Redundant Array of Inexpensive Disks (RAID) group; and

a second computer program stored on a computer readable storage medium and implemented in said second controller, said second computer program, when executed, controlling two or more disk drives of said first set of disk drive units to form a second (RAID) group.

35. A disk array system according to claim 28, further comprising:

a second set of disk drive units each comprising a disk drive formed with an interface which transfers data in accordance with the Fibre Channel protocol, and another housing installed with said second set of disk drive units.

36. A disk array system according to claim 28, further comprising:

a second set of disk drive units each comprising a disk drive formed with an interface which transfers data in accordance with the Fibre Channel protocol,

wherein said first controllers controls transfer of data to the disk drive in each of said first set of disk drive units as well as to the disk drive in each of said second set of disk drive units; and

wherein said second controller controls transfer of data to the disk drive in each of said first set of disk drive units as well as to the disk drive in each of said second set of disk drive units.

37. A disk array system according to claim 28, further comprising:

a first computer program implemented in said first controller to form a first logical volume which is adapted to store data transferred with a first Logical Unit Number from said information processing device; and

a second computer program implemented in said second controller to form a second logical volume which is adapted to store data transferred with a second Logical Unit Number from said information processing device.

38. A disk array system according to claim 28, wherein each of said first set of disk drive units is removably inserted in said expansion housing.

39. A disk array system connectable with a plurality of host computers, said disk array system comprising:

a first controller provided with a first cache memory and controlling transfer of data received from at least one of said host computers to said first cache memory and controlling transfer of data to a disk drive via said a first Fibre Channel communication path;

a second controller provided with a second cache memory and controlling transfer of data received from at least one of said host computers to said second cache memory and controlling transfer of data to a disk drive via a second Fibre Channel communication path;

a second controller provided with a second cache memory and controlling transfer of data to a disk drive via a second Fibre Channel communication path;

an expansion housing comprising a plurality of disk drive units,

wherein each of said disk drive units comprises a disk drive adapted to receive data in accordance with a Serial ATA protocol and a converter adapted to convert between the Serial ATA protocol and a Fibre Channel protocol,

wherein said converter in each of said disk drive units is coupled to a first circuit of said first Fibre Channel communication path and a second circuit of said second Fibre Channel communication path,

wherein each of said first circuit of said first Fibre Channel communication path and said second circuit of said second Fibre Channel communication path comprises a function of bypassing a failed disk drive.

40. A disk array system according to claim 39, wherein said expansion housing comprises a plurality of power supply modules, each of said power supply modules controlling to supply power to said disk drive units.

41. a disk array system according to claim 39, wherein said expansion housing further comprises a power supply module, said power supply module controlling to supply power module controlling to supply power to said disk drive units.

42. A disk array system according to claim 39, wherein said converters of each of said disk drive units is adapted to receive data from said first controller as well as said second controller and to transfer data to said disk.

43. A disk array system according to claim 39, further comprising:

another housing;

wherein said first and second circuits are a plurality of port bypass circuits

wherein said another housing is provided with said first controller and said second controller,

wherein said expansion housing is provided with said plurality of port bypass circuits.

44. A disk array system according to claim 39, further comprising:

a first computer program implemented in said first controller to form a first Redundant Array of Inexpensive Disks group with two or more of said disk drive units; and

a second computer program implemented in said second controller to form a second Redundant Array of Inexpensive Disks group with two or more of said disk drive units.

45. A disk array system according to claim 39, further comprising:

a first computer program implemented in said first controller to form a first logical volume which is adapted to stored data transferred with a first Logical Unit Number from said information processing; and

a second computer program implemented in said second controller to form a second logical volume which is adapted to store data transferred with a second Logical Unit Number from said information processing device.

46. A disk array system according to claim 39, wherein each of said disk drive units is removably inserted in said expansion housing.

47. A disk array system connectable with a host computer comprising:

a first disk controller adapted to control transfer of data received from said host computer;

a second disk controller adapted to control transfer of data received from said host computer; and

an expansion housing comprising a first set of disk drive units each provided with a disk drive which includes an interface adapted to transfer signals in accordance with a Serial ATA protocol and a converter coupled to said first and second disk controllers and adapted to execute reception of signals in accordance with a Fibre Channel protocol and transmission of signals in accordance with the Serial ATA protocol.

48. A disk array system according to claim 47, wherein said expansion housing comprises a first circuit coupled to said first disk controller and a second circuit coupled to said second disk controller, wherein said converter in one of said disk drive units is coupled to said first disk controller via said first circuit as well as to said second disk controller via said second circuit.

49. A disk array system according to claim 47, further comprising:

another housing which is installed with said first disk controller and said second disk controller;

wherein said expansion housing comprises a circuit board formed with a plurality of circuits and coupled to said converter of each of said first set of disk drive units.

50. A disk array system according to claim 47, further comprising:

a first computer program implemented in said first disk controller to form a first group of Redundant Array of Inexpensive Disks with two or more of said first set of disk drive units; and

a second computer program implemented in said first disk controller to form a second group of Redundant Array of Inexpensive Disks with two or more of said first set of disk drive units.

51. A disk array system according to claim 47, further comprising:

a second set of disk units including a disk drive provided with an interface adapted to the Fibre Channel protocol and storing data according to the Fibre Channel protocol; and

another housing installed with said second set of disk drive units and a plurality of power supply modules, each of said power supply modules controlling to supply power to said second set of disk drive units.

52. A disk array system according to claim 51,

wherein said first disk controller controls transfer of data from/to said disk drive in each of said first set of disk drive units and controls transfer of data from/to said disk drive in each of said second set of disk drive units,

wherein said second disk controller controls transfer of data from/to said disk drive in each of said first set of disk drive units and controls transfer of data from/to said disk drive in each of said second set of disk drive units.

53. A disk array system according to claim 47,

wherein said first disk controller controls transfer of data from/to said disk drive in one of said first set of disk drive units via a first Fibre Channel- Arbitrated Loop,

wherein said second disk controller controls transfer of data from/to said disk drive in one of said first set of disk drive units via a second Fibre Channel-Arbitrated Loop,

54. A disk array system according to claim 47, further comprising:

a first computer program implemented in said first disk controller to form a first group of Redundant Array of Inexpensive Disks with two or more of said first set of disk drive units; and

a second computer program implemented in said second disk controller to form a second group of Redundant Array of Inexpensive Disks with two or more of said first set of disk drive units.

55. A disk array system according to claim 47, further comprising:

a first computer program implemented in said first disk controller to form a first Logical Unit Number from said host computer; and

a second computer program implemented in said second disk controller to form a second logical volume, which is adapted to store data transferred with a second Logical Unit Number from said host computer.

56. A disk array system according to claim 47, wherein each of said first set of disk drive units is removably inserted in said expansion housing.

57. A disk array system connectable to a plurality of host computers via a network, comprising:

a first disk controller adapted to control transfer of data received from at least one of said host computers;

a second disk controller adapted to control transfer of data received from at least one of said host computers; and

an expansion housing comprising a first set of disk drive units each provided with a disk drive, which includes an interface of a Serial ATA protocol, and a converter coupled to said first disk controller via a first Fibre Channel-Arbitrated Loon and to a second disk controllers via a second Fibre Channel-Arbitrated Loop and adapted to execute reception of a command of a Fibre Channel protocol and transmission of a command of a Serial ATA protocol, said disk drive receiving the command via said converter;

wherein each of a first circuit of said first Fibre Channel-Arbitrated Loop and a second circuit of said second Fibre Channel-Arbitrated Loop comprises a function of bypassing a failed disk drive.

58. A disk array system according to claim 57, wherein said expansion housing comprises said first circuit and said second circuit.

59. A disk array system according to claim 57, further comprising:

another housing which is installed with said first disk controller and said second disk controller;

wherein said expansion housing comprises a circuit board formed with said first and second circuits and coupled to said converter of each of said first set of disk drive units.

60. A disk array system according to claim 57, further comprising:

a first, computer program implemented in said first disk controller to form a group of Redundant Array of Inexpensive Disks with two or more of said first set of disk drive units; and

a second computer program implemented in said second disk controller, to form a group of Redundant Array of Inexpensive Disks with two or more of said first set of disk drive units.

61. A disk array system according to claim 57, further comprising:

a second set of disk drive units each including a disk drive provided with an interface adapted to the Fibre Channel protocol and storing data according to the Fibre Channel protocol; and

another housing installed with said second set of disk drive units.

62. A disk array system according to claim 61,

wherein either of said first and second disk controllers controls transfer of data from/to said disk drive in each of said first set of disk drive units as well as in each of said second set of disk drive units.

63. A disk array system according to claim 57, further comprising:

a first computer program implemented in said first disk controller to form a first logical volume adapted to store data transferred with a first Logical Unit Number from at least one of said host computers and

a second computer program implemented in said second disk controller to form a second logical volume adapted to store data transferred with a second Logical Unit Number from at least one of said host computers.

64. A disk array system according to claim 57, wherein each of said first set of disk drive units is removably inserted in said expansion housing.

65. A disk array system connectable to a plurality of information processing devices comprising:

a first housing installed with a first and a second disk controllers adapted to be coupled to said information processing devices to control transfer of data between the disk array system and the coupled information processing devices; and

a second housing installed with a plurality of disk drive units each with a disk drive provided with an interface accessible in accordance with a Serial ATA protocol,

wherein each of said disk drive units is further provided with a converter which couples to both a first circuit of a first Fibre Channel-Arbitrated Loop of said first disk controller and a second circuit of a second Fibre Channel-Arbitrated Loop of said second disk controller and, when the disk drive unit is accessed in accordance with the Fibre Channel protocol, converts the protocol to the Serial ATA protocol whereby received data is transferred to the disk drive via the converter in accordance with the Serial ATA protocol,

wherein each of said first circuit and said second circuit comprises a function of bypassing a failed disk drive.

66. A disk array system connectable to a plurality of host computers via a network wherein said network includes a communication path which transfers data in accordance with a Fibre Channel protocol, said disk array system comprising:

a first housing installed with a first and a second disk controllers each adapted to be coupled to said host computers so as to control transfer of data between the disk array system and the coupled host computers; and

a second housing installed with a plurality of disk drive units each including a disk drive provided with an interface accessible in accordance with a Serial ATA protocol,

wherein each of said disk drive units is further provided with a converter which are coupled to both a first circuit of a first Fibre Channel communication medium coupled to said first disk controller and a second circuit of a second Fibre Channel communication medium coupled to said second disk controller and, when the disk drive unit is accessed in accordance with the Fibre Channel protocol, coverts the protocol to the Serial ATA protocol whereby received data is transferred to the disk drive via the converter in accordance with the Serial ATA protocol,

wherein each of said first circuit and said second circuit comprises a function of bypassing a failed disk drive.

67. A disk array system connectable with a plurality of host computers via a network, said disk array system comprising:

a first disk controller comprising a first cache memory and controlling transfer of data from the connected host computer to write received data to said first cache memory;

a second disk controller comprising a second cache memory and controlling transfer of data from the connected host computer to write received data to said second cache memory;

a plurality of converters which performs conversion of protocol between a Fibre Channel protocol and a Serial ATA protocol; and

an expansion housing installed with a plurality of disk drive units, each disk drive unit provided with both a converter of said plurality of converters and a disk drive having an interface of the Serial ATA protocol,

wherein, when one of said first and second disk controllers transmits data from its cache memory to one of the disk drive units in accordance with the Fibre Channel protocol, the transferred data is converted to the Serial ATA protocol by said converter and the converted data is supplied to said disk drive of one of the disk drive units for storing the received data.

68. A disk array system connectable to a host computer, said disk array system comprising:

a first housing installed with a first and a second disk controllers adapted to control transfer of data received from said host computer; and

a second housing installed with a set of disk drive units, each provided with a disk drive adapted to a Serial ATA protocol and a converter which is coupled to both a first circuit coupled to said first disk controller and a second circuit coupled to said second disk controller and, under control of either of said first and second disk controllers, executes reception of a command of the Fibre Channel protocol and transfer of a command of the Serial ATA protocol to the disk drive, whereby data received from said host computer is transferred to the disk drive in accordance with the Serial ATA protocol via said converter and stored in the disk drive,

wherein each of said first circuit and said second circuit comprises a function of bypassing a failed disk drive.