Input/output controller providing preventive maintenance information regarding a spare I/O unit

• US 6,324,655 B1
• Filed: 03/02/1998
• Issued: 11/27/2001
• Est. Priority Date: 09/20/1990
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Matoba, Tatsuo, Yorimitsu, Keiichi
• Primary Examiner(s): LE, DIEU MINH T
• Application Number:
  US09/034,010
• Time in Patent Office: 1,366 Days
• Field of Search: 714/7, 714/6, 714/2, 714/710, 714/711, 714/42, 714/165
• US Class Current: 714/6.32
• CPC Class Codes: G06F 11/004 Error avoidance G06F11/07 and subgroups take precedence
• CPC Class Codes: G06F 11/10 Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's
• CPC Class Codes: G06F 11/1008 in individual solid state devices G06F11/1004 takes precedence
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: G06F 11/2205 using arrangements specific to the hardware being tested

Abstract

A I/O controller which is connected to a plurality of I/O units and one spare I/O unit, controls a plurality of I/O units based on a command from a master unit, and allows a spare I/O unit to be used in place of an I/O unit where an abnormality is found, when an abnormality is found in any of a plurality of I/O units. This I/O controller gives a decision about normality at a time interval not in use for an operation when no command from a master unit (10) is being processed, after selecting I/O units (30) or a spare I/O unit (31). When it gives a decision of abnormality, the controller stores information about the abnormality in preventive maintenance information storage register (25) as preventive maintenance information.

Claims

1. An array storage system coupled to a host unit and comprising:

logical devices, each logical device comprising;

a spare storage device, and

data storage devices;

array-type disk controllers, provided in a pair and in parallel and coupled to the logical devices and to the host unit, each of said array-type controllers simultaneously and independently controlling a respective one of said logical devices to execute a command issued by the host unit and to determine whether each of the spare storage device and the data storage devices provided in the respective one of said logical devices is one of normal and abnormal, each of said array-type disk controllers controlling said data storage devices provided in the respective one of said logical devices if the each of said data storage devices provided in the respective one of said logical devices is normal, and controlling the spare storage device and remaining of said normal data storage devices provided in the respective one of said logical devices if one of the data storage devices provided in the respective one of the logical devices is abnormal; and

power supply means for supplying power to each of said data storage devices and said spare storage device and for maintaining each of said data storage devices and said spare storage device provided in each of said logical devices in ready status, wherein the spare storage device stores data previously stored in the one of the data storage devices being abnormal, and reconstructed by a reconstruction process, and wherein data is not stored in the spare storage device if said data storage devices are normal.

2. The array storage system as recited in claim 1, wherein data defined by a command issued by the host unit are written in a read from the data storage devices in a block of 8 bytes simultaneously.

3. The array storage system as recited in claim 1, wherein the each logical device further comprises a parity disk drive, the power supply means maintains the parity disk drive in ready status, and parity is written in and read from the parity disk drive at the same time the data are written in and read from the data storage devices.

4. The array storage system as recited in claim 1, wherein each of the array-type controllers executes a patrol operation to determine whether each of the data storage devices and the spare disk device in each of the logical devices is one of normal and abnormal.

5. An array storage system coupled to a host unit issuing an operation command, said array storage system comprising:

storage devices comprising;

a spare storage device, and

data storage devices;

an operation controller controlling a read operation on said storage devices, said operation controller controlling said data storage devices if said data storage devices are normal and without one of a hard error, a read error, and both the hard error and the read error, and controlling the spare storage device and remaining of said data storage devices which are normal if one of a hard error, a read error, and both are found in one of the storage devices, said operation controller comprising;

a subordinate unit I/O controller connected to said storage devices,

a host unit interface controller, operatively connected to said host unit and said subordinate unit I/O controller, receiving said operation command issued from said host unit and forwarding said operation command to said storage devices,

checking means for checking a normality of data in said storage devices, based on a signal obtained by reading data and the error detection code concurrently from said storage devices,

controlling means for controlling at least one of said storage devices based on said operation command input from said host interface controller via said subordinate unit I/O controller, said controlling means controlling said data storage devices only, if a normality of data is found in all said data storage devices by said checking means and controlling remaining normal data storage devices and said spare storage device if an abnormality is found in any of said data storage devices by said checking means, and controlling, via said subordinate unit I/O controller, one of said selected data storage devices and said spare storage device, on the basis of said operation command input from said host unit via said host unit interface controller,

decision means for deciding whether at least one of said data storage devices and said spare storage device operate normally if said controlling means is not processing said operation command input from said host unit via said host unit interface controller, and

an information storage register temporarily storing information regarding an abnormality if an abnormality of said data storage devices and said spare storage device is found by said decision means; and

power supply means for supplying power to each of said data storage devices, and said spare storage device, and for maintaining each of said storage devices in ready status.

6. The array storage system as claimed in claim 5, wherein said spare storage device outputs a hard error signal if data is not normally written in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on said hard error signal from said spare storage device.

7. The array storage system as claimed in claim 6, wherein said spare storage device outputs the read error signal if data written during a write operation on said spare storage device is not normally read during the read operation in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

8. The array storage system as claimed in claim 6, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

9. The array storage system as claimed in claim 6, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said spare storage device.

10. The array storage system as claimed in claim 6, wherein if a command is not executed within a specified time after an execution of a command from a host unit, said decision controller outputs a decision about abnormality for one selected storage device of the storage devices, based on one of a presence and an absence of the hard error, after carrying out a patrol seek operation wherein each head of data disk drives of said storage devices and said at least one of said plurality of data disk drives of said storage devices storing parity data, which comprise said one selected storage device, is moved a specified distance.

11. The array storage system as claimed in claim 6, further comprising:

means for determining that said controlling means is not processing a command input from said host unit via said channel interface controller; and

a patrol timer register for counting a predetermined time interval in accordance with said determining means,

wherein said decision means outputs a decision about normality in one of said selected storage device and said spare storage device after said patrol timer register counts up the predetermined time interval.

12. The array storage system as claimed in claim 6, wherein said array storage system comprises more than one said host unit interface controller, said checking means, said information storage register, said controlling means, said decision means, and said subordinate unit interface controller, which are placed in a shared connection with a plurality of storage devices.

13. The array storage system as claimed in claim 5, wherein said decision means allows said spare storage device to carry out a write operation of data if a first seek operation is performed and completed in a normal manner, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said storage devices.

14. The array storage system as claimed in claim 5, wherein the storage devices are disk drives.

15. The array storage system as claimed in claim 14, wherein the disk drives are magnetic disk drives.

16. An array storage system comprising:

storage devices comprising;

a spare storage device, and

data storage devices;

an operation controller controlling a read operation on said storage devices, said operation controller controlling said data storage devices if said data storage devices are normal and without one of a hard error, a read error, and both the hard error and the read error, and controlling the spare storage device and other of said data storage devices which are normal if one of a hard error, a read error, and both are found in one of the storage devices; and

means for carrying out a seek operation if said operation controller is not processing a command input from an external unit, coupled to the array storage system, to said operation controller, wherein the spare storage device stores data previously stored in the one of the data storage devices experiencing one of a hard error, a read error, and both, and reconstructed by a reconstruction process, and wherein data are not stored in the spare storage device if said data storage devices are normal and without error, wherein the spare storage device is separate from the data storage devices.

17. The array storage system as claimed in claim 16 wherein the storage devices are disk drives.

18. The array storage system as claimed in claim 17, wherein the disk drives are magnetic disk drives.

19. An array storage system comprising:

storage devices comprising;

a spare storage device, and

data storage devices;

an operation controller controlling a read operation on said storage devices, said operation controller controlling said data storage devices and said first storage device if said data storage devices and said first storage device are normal and without one of a hard error, a read error, and both the hard error and the read error, and controlling the first storage device, the spare storage device and other of said data storage devices which are normal if one of a hard error, a read error, and both are found in one of the storage devices, said operation controller comprising;

a subordinate unit I/O controller connected to said storage devices,

an external unit interface controller, operatively connected to said external unit and said subordinate unit I/O controller, receiving said operation command issued from said external unit and forwarding said operation command to said storage devices,

checking means for checking a normality of data in said storage devices, based on a signal obtained by reading data and the error detection code concurrently from said storage devices,

controlling means for controlling at least one of said storage devices based on said operation command input from said external interface controller via said subordinate unit I/O controller, said controlling means controlling said data storage devices only, if a normality of data is found in all said data storage devices by said checking means and controlling remaining normal data storage devices and said spare storage device if an abnormality is found in any of said data storage devices by said checking means, and controlling, via said subordinate unit I/O controller, one of said selected data storage devices and said spare storage device, on the basis of said operation command input from said external unit via said external unit interface controller,

decision means for deciding whether at least one of said data storage devices and said spare storage device operate normally if said controlling means is not processing said operation command input from said external unit via said external unit interface controller, and

an information storage register temporarily storing information regarding an abnormality if an abnormality of said data storage devices and said spare storage device is found by said decision means; and

means for carrying out a seek operation if said operation controller is not processing a command input from an external unit, coupled to the array storage system, to said operation controller.

20. The array storage system as claimed in claim 19, wherein said spare storage device outputs the read error signal if data written during a write operation on said spare storage device is not normally read during the read operation in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

21. The array storage system as claimed in claim 19, wherein said spare storage device outputs a hard error signal if the seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

22. The array storage system as claimed in claim 19, wherein said spare storage device outputs a hard error signal if the seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said spare storage device.

23. The array storage system as claimed in claim 19, wherein said decision means allows said spare storage device to carry out a write operation of data if a first seek operation is performed and completed in a normal manner, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said storage devices.

24. The array storage system as claimed in claim 19, wherein if a command is not executed within a specified time after an execution of a command from the external unit, said decision controller outputs a decision about abnormality for one selected storage device of the storage devices, based on one of a presence and an absence of the hard error, after carrying out a patrol seek operation wherein each head of data disk drives of said storage devices is moved a specified distance.

25. The array storage system as claimed in claim 19, further comprising:

means for determining that said controlling means is not processing a command input from said external unit via said external unit interface controller; and

a patrol timer register for counting a predetermined time interval in accordance with said determining means,

wherein said decision means outputs a decision about normality in one of said selected storage device and said spare storage device after said patrol timer register counts up the predetermined time interval.

26. The array storage system as claimed in claim 19, wherein said array storage system comprises more than one said external unit interface controller, said checking means, said information storage register, said controlling means, said decision means, and said subordinate unit interface controller, which are placed in a shared connection with a plurality of storage devices.

27. An array storage apparatus coupled to a host unit issuing a command, said array storage apparatus comprising:

a logical storage device comprising physical storage devices, said physical storage devices comprising;

a spare physical storage device, and

physical data storage devices; and

an array controller, coupled to the logical storage device, and comprising an information storage register storing information about an abnormality of said physical data storage devices belonging to said logical storage device, said array controller controlling a read operation on said logical storage device and transmitting the information stored in said information storage register to the host unit, said command issued by the host unit indicating the read operation on said logical device where the information is stored in said register, wherein the spare storage device stores data previously stored in one of the physical data storage devices experiencing the abnormality, and reconstructed by a reconstruction process, and wherein data are not stored in the spare storage device if said physical data storage devices are not experiencing the abnormality, wherein the spare physical storage device is separate from the physical data storage devices.

28. The array storage apparatus as claimed in claim 27, wherein the storage devices are magnetic storage devices.

29. An array storage apparatus coupled to a host unit issuing a command, said array storage apparatus comprising:

a logical storage device comprising physical storage devices, said physical storage devices comprising;

a spare physical storage device, and

physical data storage devices; and

an array controller, coupled to the logical storage device and comprising an information storage register storing information about an abnormality of said physical storage devices belonging to said logical storage device, said array controller controlling a read operation on said logical storage device and transmitting the information stored in said information storage register to the host unit, said command issued by the host unit indicating the read operation on said logical device where the information is stored in said register, said array controller further comprising;

a subordinate unit I/O controller connected to said storage devices,

a host unit interface controller, operatively connected to said host unit and said subordinate unit I/O controller, receiving said operation command issued from said host unit and forwarding said operation command to said storage devices,

checking means for checking a normality of data in said storage devices, based on a signal obtained by reading data and the error detection code concurrently from said storage devices,

controlling means for controlling at least one of said storage devices based on said operation command input from said host interface controller via said subordinate unit I/O controller, said controlling means controlling said data storage devices only, if a normality of data is found in all said data storage devices by said checking means and controlling remaining normal data storage devices and said spare storage device if an abnormality as found in any of said data storage devices by said checking means, and controlling, via said subordinate unit I/O controller, one of said selected data storage devices and said spare storage device, on the basis of said operation command input from said host unit via said host unit interface controller,

decision means for deciding whether at least one of said data storage devices and said spare storage device operate normally if said controlling means is not processing said operation command input from said host unit via said host unit interface controller, and

an information storage register temporarily storing information regarding an abnormality if an abnormality of said data storage devices and said spare storage device is found by said decision means.

30. The array storage apparatus as claimed in claim 29, wherein said spare storage device outputs a hard error signal if data is not normally written in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on said hard error signal from said spare storage device.

31. The array storage apparatus as claimed in claim 30, wherein said spare storage device outputs the read error signal if data written during a write operation on said spare storage device is not normally read during the read operation in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

32. The array storage apparatus as claimed in claim 30, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

33. The array storage apparatus as claimed in claim 30, wherein the storage devices are magnetic storage devices.

34. The array storage apparatus as claimed in claim 29, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said spare storage device.

35. The array storage apparatus as claimed in claim 29, wherein said decision means allows said spare storage device to carry out a write operation of data if a first seek operation is performed and completed in a normal manner, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said storage devices.

36. The array storage system as claimed in claim 35, wherein if a command is not executed within a specified time after an execution of a command from a host unit, said decision controller outputs a decision about abnormality for one selected storage device of the storage devices, based on one of a presence and an absence of the hard error, after carrying out a patrol seek operation wherein each head of data disk drives of said storage devices is moved a specified distance.

37. The array storage apparatus as claimed in claim 36, wherein the storage devices are magnetic storage devices.

38. The array storage apparatus as claimed in claim 29, wherein the storage devices are magnetic storage devices.

39. An array storage apparatus coupled to a host unit issuing a command, said array controller comprising:

logical storage devices, each of the logical storage devices comprising;

physical storage devices comprising;

a spare physical storage device being a spare storage device, and

physical data storage devices; and

an array controller, coupled to the logical storage devices and comprising an information storage register storing information about an abnormality of said physical storage devices belonging to each of said logical storage devices, said array controller controlling a read operation on said logical storage devices independently and transmitting the information storage in said information storage register to the host unit, said command issued by the host unit indicating the read operation to one of said logical devices where the information has been stored in said register, wherein the spare storage device stores data previously stored in one of the physical data storage devices experiencing the abnormality, and reconstructed by a reconstruction process, and wherein data are not stored in the spare storage device if said physical data storage devices are not experiencing the abnormality, wherein said spare physical storage device is separate from said physical data storage devices.

40. An array storage apparatus coupled to a host unit issuing a command, said array controller comprising:

logical storage devices, each of the logical storage devices comprising;

physical storage devices comprising;

a spare physical storage device, and

physical data storage devices; and

array controllers, providing in a pair and in parallel, and coupled to the physical storage devices, controlling a read operation on said logical storage devices independently, said array controllers comprising;

an information storage register storing information about an abnormality of said physical storage devices belonging to each of said logical storage devices, wherein said array controllers transmitting the information storage in said information storage register to the host unit, said command issued by the host unit indicating the read operation to one of said logical devices where the information has been stored in said register,

a subordinate unit I/O controller connected to said storage devices,

a host unit interface controller, operatively connected to said host unit and said subordinate unit I/O controller, receiving said operation command issued from said host unit and forwarding said operation command to said storage devices,

checking means for checking a normality of data in said storage devices, based on a signal obtained by reading data and the error detection code concurrently from said storage devices,

controlling means for controlling at least one of said storage devices based on said operation command input from said host interface controller via said subordinate unit I/O controller, said controlling means controlling said data storage devices only, if a normality of data is found in all said data storage devices by said checking means and controlling remaining normal data storage devices and said spare storage device if an abnormality is found in any of said data storage devices by said checking means, and controlling, via said subordinate unit I/O controller, one of said selected data storage devices and said spare storage device, on the basis of said operation command input from said host unit via said host unit interface controller,

decision means for deciding whether at least one of said data storage devices and said spare storage device operate normally if said controlling means is not processing said operation command input from said host unit via said host unit interface controller, and

an information storage register temporarily storing information regarding an abnormality if an abnormality of said data storage devices and said spare storage device is found by said decision means.

41. The array storage apparatus as claimed in claim 40, wherein said spare storage device outputs a hard error signal if data is not normally written in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on said hard error signal from said spare storage device.

42. The array storage apparatus as claimed in claim 41, wherein said spare storage device outputs the read error signal if data written during a write operation on said spare storage device is not normally read during the read operation in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

43. The array storage apparatus as claimed in claim 41, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

44. The array storage apparatus as claimed in claim 41, wherein the storage devices are magnetic storage devices.

45. The array storage apparatus as claimed in claim 40, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said spare storage device.

46. The array storage apparatus as claimed in claim 40, wherein said decision means allows said spare storage device to carry out a write operation of data if a first seek operation is performed and completed in a normal manner, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said storage devices.

47. The array storage system as claimed in claim 46, wherein if a command is not executed within a specified time after an execution of a command from a host unit, said decision controller outputs a decision about abnormality for one selected storage device of the storage devices, based on one of a presence and an absence of the hard error, after carrying out a patrol seek operation wherein each head of data disk drives of said storage devices is moved a specified distance.

48. The array storage apparatus as claimed in claim 40, wherein the storage devices are magnetic storage devices.

49. An array storage apparatus coupled to a host unit issuing a command and accessible to a logical storage device comprising physical storage devices, a first one of the physical storage devices storing an error correction code, a spare one of the physical storage devices being a spare storage device, and each of remaining of the physical storage devices storing data, said array storage apparatus comprising:

an operation controller controlling a read operation on said storage devices, said operation controller controlling said data storage devices and said first one of the physical storage devices if said remaining of the storage devices and said first one of the storage devices are normal and do not contain one of a hard error, a read error, and both of the hard error and the read error, and controlling other of said remaining storage devices, the first one of the storage devices, and said spare of the storage devices if one of said remaining storage devices contains one of a hard error, a read error, and both the hard error and the read error; and

means for instructing a seek operation to said physical storage devices if said operation controller is not processing a command input from an external unit to said operation controller, wherein the spare storage device stores data previously stored in the one of the remaining data storage devices experiencing one of a hard error, a read error, and both, and reconstructed by a reconstruction process, and wherein data are not stored in the spare storage device if said remaining data storage devices are normal and without error, wherein said spare one of said physical storage devices being separate from said first one of said physical storage devices and separate from each of the remaining of the physical storage devices.

50. The array storage apparatus as claimed in claim 49, wherein the storage devices are magnetic storage devices.

51. An array storage apparatus coupled to a host unit issuing a command and accessible to a logical storage device comprising physical storage devices, a first one of the physical storage devices storing an error correction code, a spare one of the physical storage devices being a spare storage device, and each of remaining of the physical storage devices storing data, said array storage apparatus comprising:

an operation controller controlling a read operation on said storage devices, said operation controller controlling said data storage devices and said first one of the physical storage devices if said remaining of the storage devices and said first one of the storage devices are normal and do not contain one of a hard error, a read error, and both of the hard error and the read error, and controlling other of said remaining storage devices, the first one of the storage devices, and said spare of the storage devices if one of said remaining storage devices contains one of a hard error, a read error, and both the hard error and the read error, said operation controller comprising;

a subordinate unit I/O controller connected to said storage devices,

a host unit interface controller, operatively connected to said host unit and said subordinate unit I/O controller, receiving said operation command issued from said host unit and forwarding said operation command to said storage devices,

checking means for checking a normality of data in said storage devices, based on a signal obtained by reading data and the error detection code concurrently from said storage devices,

controlling means for controlling at least one of said storage devices based on said operation command input from said host interface controller via said subordinate unit I/o controller, said controlling means controlling said data storage devices only, if a normality of data is found in all said data storage devices by said checking means and controlling remaining normal data storage devices and said spare storage device if an abnormality is found in any of said data storage devices by said checking means, and controlling, via said subordinate unit I/O controller, one of said selected data storage devices and said spare storage device, on the basis of said operation command input from said host unit via said host unit interface controller,

decision means for deciding whether at least one of said data storage devices and said spare storage device operate normally if said controlling means is not processing said operation command input from said host unit via said host unit interface controller, and

an information storage register temporarily storing information regarding an abnormality if an abnormality of said data storage devices and said spare storage device is found by said decision means; and

means for instructing a seek operation to said physical storage devices if said operation controller is not processing a command input from an external unit to said operation controller.

52. The array storage apparatus as claimed in claim 51, wherein said spare storage device outputs a hard error signal if data is not normally written in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on said hard error signal from said spare storage device.

53. The array storage apparatus as claimed in claim 52, wherein said spare storage device outputs the read error signal if data written during a write operation on said spare storage device is not normally read during the read operation in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

54. The array storage apparatus as claimed in claim 52, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

55. The array storage apparatus as claimed in claim 52, wherein the storage devices are magnetic storage devices.

56. The array storage apparatus as claimed in claim 51, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said spare storage device.

57. The array storage apparatus as claimed in claim 51, wherein said decision means allows said spare storage device to carry out a write operation of data if a first seek operation is performed and completed in a normal manner, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said storage devices.

58. The array storage system as claimed in claim 57, wherein if a command is not executed within a specified time after an execution of a command from a host unit, said decision controller outputs a decision about abnormality for one selected storage device of the storage devices, based on one of a presence and an absence of the hard error, after carrying out a patrol seek operation wherein each head of data disk drives of said storage devices, which comprise said one selected storage device, is moved a specified distance.

59. The array storage apparatus as claimed in claim 51, wherein the storage devices are magnetic storage devices.

60. An array storage apparatus coupled to a host unit issuing a command and accessible to a logical storage device comprising physical storage devices, a first one of the physical storage devices storing an error correction code, a spare one of the physical storage devices being a spare storage device, said array storage apparatus comprising:

an array controller coupled to the logical storage device and comprising an information storage register storing information about an abnormality of said physical storage devices belonging to said logical storage device, said array controller controlling a read operation on said logical storage device, said array controller transmitting the information stored in said information storage register to the host unit, said command issued by the host unit indicating the operation to said logical device where the information has been stored in said register, wherein the spare storage device stores data previously stored in one of the remaining physical data storage devices experiencing the abnormality, and reconstructed by a reconstruction process, and wherein data are not stored in the spare storage device if said remaining physical data storage devices are not experiencing the abnormality, wherein said spare one of said physical storage devices being separate from said first one of said physical storage devices and separate from each of remaining of the physical storage devices.

61. The array storage apparatus as claimed in claim 60, wherein the storage devices are magnetic storage devices.

62. An array storage apparatus coupled to a host unit issuing a command and accessible to a logical storage device comprising physical storage devices, a first one of the physical storage devices storing an error correction code, a spare one of the physical storage devices being a spare storage device, said array storage apparatus comprising:

an array controller coupled to the logical storage device and comprising an information storage register storing information about an abnormality of said physical storage devices belonging to said logical storage device, said array controller controlling a read operation on said logical storage device, said array controller transmitting the information stored in said information storage register to the host unit, said command issued by the host unit indicating the operation to said logical device where the information has been stored in said register, wherein the spare storage device stores data previously stored in one of the remaining physical data storage devices experiencing the abnormality, and reconstructed by a reconstruction process, and wherein data are not stored in the spare storage device if said remaining physical data storage devices are not experiencing the abnormality, wherein said array controller further comprises;

a subordinate unit I/O controller connected to said storage devices,

a host unit interface controller, operatively connected to said host unit and said subordinate unit I/O controller, receiving said operation command issued from said host unit and forwarding said operation command to said storage devices,

checking means for checking a normality of data in said storage devices, based on a signal obtained by reading data and the error detection code concurrently from said storage devices,

controlling means for controlling at least one of said storage devices based on said operation command input from said host interface controller via said subordinate unit I/O controller, said controlling means controlling said data storage devices only, if a normality of data is found in all said data storage devices by said checking means and controlling remaining normal data storage devices and said spare storage device if an abnormality is found in any of said data storage devices by said checking means, and controlling, via said subordinate unit I/O controller, one of said selected data storage devices and said spare storage device, on the basis of said operation command input from said host unit via said host unit interface controller, and

decision means for deciding whether at least one of said data storage devices and said spare storage device operate normally if said controlling means is not processing said operation command input from said host unit via said host unit interface controller, said information storage register temporarily storing information regarding an abnormality if an abnormality of said data storage devices and said spare storage device is found by said decision means.

63. The array storage apparatus as claimed in claim 62, wherein said spare storage device outputs a hard error signal if data is not normally written in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on said hard error signal from said spare storage device.

64. The array storage apparatus as claimed in claim 63, wherein said spare storage device outputs the read error signal if data written during a write operation on said spare storage device is not normally read during the read operation in said spare storage device, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

65. The array storage apparatus as claimed in claim 63, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the read error signal from said spare storage device.

66. The array storage apparatus as claimed in claim 63, wherein the storage devices are magnetic storage devices.

67. The array storage apparatus as claimed in claim 62, wherein said spare storage device outputs a hard error signal if a seek operation is not carried out normally, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said spare storage device.

68. The array storage apparatus as claimed in claim 62, wherein said decision means allows said spare storage device to carry out a write operation of data if a first seek operation is performed and completed in a normal manner, and

wherein said decision means outputs a decision about an abnormality based on the hard error signal from said storage devices.

69. The array storage system as claimed in claim 68, wherein if a command is not executed within a specified time after an execution of a command from a host unit, said decision controller outputs a decision about abnormality for one selected storage device of the storage devices, based on one of a presence and an absence of the hard error, after carrying out a patrol seek operation wherein each head of data disk drives of said storage devices is moved a specified distance.

70. The array storage apparatus as claimed in claim 62, wherein the storage devices are magnetic storage devices.