Recording device

Abstract: A recording device which improves a response time to write data by reporting to a host computer the completion of writing operation prior to the completion of writing redundancy data. Data writing command information from the host computer is stored in a command/status memory backed up by a power source in an array controller, and the completion of writing operation is reported to the host computer at the time of the completion of writing updated data prior to the completion of writing redundancy data. Redundancy data is written as a background process. If redundancy data could not be written due to any abnormality of the power source or the like, such redundancy data may be generated from the data in other disk units of the same redundancy group in accordance with writing command information stored in the command/status memory, thereby completing the writing of redundancy data.

Description: The present invention relates to a recording device comprising primary recording units, stand-by recording units and a maintenance diagnosis means. Fig. 1 illustrates the constitution of a conventional array-type recording device which has been disclosed in Japanese Patent Laid-Open Publication No. 236714/90. In Fig. 1, the reference numeral 1 designates a host computer; 2 a host interface (hereinafter called Host I/F) which serves as a buffer between host computer 1 and an array controller 13; 3 a microprocessor adapted to control the whole array controller 13; 4 a memory; 5 an ECC engine adapted to generate redundancy data and reconstruct data; 6 a data path commonly connected to host I/F2, microprocessor 3, memory 4 and ECC engine 5; 7 a CE panel; and 8a through 8e channel controllers. CE panel 7 and the plurality of channel controllers 8a - 8e are connected to data path 6. The reference numerals 9a - 9e designate disk units; and 10 channels, through which the plurality of disk units 9a - 9e are connected to channel controllers 8a - 8e; 11 stand-by disks; 12 spare channels, through which plurality of stand-by disks 11 are connected to channel controller 8; and 13 an array controller for controlling plurality of disk units 9a - 9e and stand-by disk 11. Operation of the illustrated recording device will next be explained. In Fig. 1, data are recorded and reproduced by host computer 1 through host I/F 2. Upon storage of data, commands and data from host computer 1 are stored in memory 4 by way of data path 6. Upon reproduction of data, the data stored in memory 4 is transferred to host computer 1 by way of host I/F2. The conventional device has a problem in that, during a process of replacement of disks in the case of abnormality, if a stand-by disk used for replacement is damaged, the performance of the system is degraded. PATENT ABSTRACTS OF JAPAN, Vol. 11, No. 292 (E-543), 19 September 1987, discloses an auxiliary monitor system having the purpose to detect the trouble of an auxiliary processor system in an earlier time and to securely switch a present system to an auxiliary one by always monitoring the normalcy of the auxiliary system through the use of an exclusively used memory which each duplicated processor can access independently and a state display device, when the operation is normal. To this end, an auxiliary processor executes a processor diagnosis program stored in an exlusively used memory and a memory-only diagnosis program at every fixed period. When the processor or memory is decided to be normal, a state display device displays the effect, and if they are abnormal, the state display device does not display the effect. Then a present system processor executes an auxiliary monitor program stored in a further exclusively used memory or in a main memory. This monitor program reads the display on the state display device at every fixed period, decides that the auxiliary system is normal fixed period, decides that the auxiliary system is normal if the display is present, and resets the display on the state display device. If the display cannot be formed during a fixed period, the program decides that the auxiliary system is troubled, and trouble information processing is executed. It is the object of the present invention to improve a recording device comprising primary recording units, stand-by recording units and a maintenance diagnosis means in such a way that the stand-by recording units are used in an efficient manner. This object according to the invention is solved by a recording device having the features of claim 1. Preferred embodiments of this recording device are defined in the subclaims. According to the invention, a recording device comprises: (a) primary recording units for recording data; (b) stand-by recording units which are functionally identical to said primary recording units usable in place of faulty ones of said primary recording units; (c) a maintenance diagnosis means for irregularly or periodically diagnosing in a background operation said stand-by recording units to decide whether any of said stand-by recording units is faulty or not; and (d) a means for selecting and setting the number of said stand-by recording units depending on the reliability of the recording device as a result of periodical or irregular diagnosis of the primary recording units. In this way the maintenance diagnosis means is designed to periodically or non-periodically make diagnosis of such stand-by recording units replaceable with the recording units in the case of fault in any recording unit and detect abnormality of the stand-by recording units, consequently, the stand-by recording units can be used in the case of abnormality of any of the recording units and disables the faulty recording units so as to separate them from the system, thereby improving reliability. In a preferred embodiment the recording device comprises an error recording unit for recording error information at the time of recording data in and reproducing data from primary recording unit, wherein the maintenance diagnosis means decides whether any primary recording unit should be replaced with the stand-by recording units or not in accordance with the error information recorded in the error recording means. In this manner, the error recording means is designed to collect and record errror information when the system is in operation, and the maintenance diagnosis means is designed to decide if any primary recording unit in which an error exceeding a predetermined level has occured is faulty, whereby a faulty primary recording unit is replaced with stand-by recording units and the faulty primary recording unit is separated from the system. Therefore, there is no possibility of concurrent faults occurring in a plurality of primary recording units, thereby improving a system reliability. Fig. 1 illustrates the constitution of an array-type recording device according to the prior art; and Fig. 2 illustrates the constitution of a preferred embodiment of an array-type recording device according to the present invention. An embodiment of the present invention will now be explained by referring to Fig. 2. In Fig. 2, the reference numeral 1 designates a host computer; 2 a host I/F (an interface section) which serves as a buffer between host computer 1 and an array controller 13; 3 a microprocessor which controls the whole array controller 13; 4 a memory in which programs, data and the like used in microprocessor 3 are stored; 5 an ECC engine (a redundancy providing means) adapted to detect errors in data which pass through data path 6 and encode and decode the corrected data; 8a through 8e channel controllers which provide control between the array controller and disk units; 9 disk units (recording units) in which data are stored; 10a and 10b channels; 11 stand-by disks (stand-by recording units) which are spare disk units; 14 a command/status memory comprising a RAM which hold commands transmitted from host computer 1 and a status representing a processing state; 15 a cache which holds data sent from host computer 1 and data read from disk units 9, command/status memory 14 and cache 15 being backed up by a memory back-up mechanism 16 comprising a secondary power source such as a battery; 18 a power source control device for supplying power and providing control to disk units 9 and stand-by disks 11; 20 a maintenance diagnosis processor adapted to monitor, as a maintenance diagnosis means, array controller 13, disk units 9 and stand-by disks 11 and cause error information to be stored in an error storage means 19 in case of abnormality and to be displayed on a display panel 21; and 22 a remote communicating device adapted to inform a maintenance center (not shown) of error information or the like. Microprocessor 3 and memory 4 form a control section 23 and microprocessor 3 is operated by programs and data stored in memory 4 so as to control array controller 13 and the entire system. The array-type recording device illustrated in Fig. 2 has a plurality of stand-by disks 11 which replace any damaged disk units. It is to be noted that, as stand-by disks may be damaged during rest, these stand-by disks 11 are periodically or irregularly diagnosed in a background operation under the control of maintenance diagnosis processor 20 (maintenance diagnosis means). As a result, if any abnormability is detected by the diagnosis processor, such a faulty stand-by disk is disabled and separated from the system. For this reason, such situation that a disk unit is damaged during use and a stand-by disk to replace is also damaged can be avoided. Thus, an available stand-by disk is always ready for use. Maintenance diagnosis means 20 includes a means for selecting and setting the number of stand-by disks and using the result of periodical or irregular diagnosis of disk units, can reduce the number of stand-by disks when the system is found to be highly reliable, but can increase the number of stand-by disks when the system reliability drops. It is also possible to hold such stand-by disks in an immediately available state or "hot" state. Alternatively, they can be held in a "cold" state, that is power supply is off except when the diagnosis is conducted or replacement of the stand-by disk is executed, or held in combination of the "hot" and "cold" states. If the stand-by disk units are held in the "cold" condition, the stand-by disk units can be energized in accordance with a command from maintenance diagnosis processor 20 during diagnosis by way of power supply control device 18, thereby enabling the diagnosis. After the completion of diagnosis, the stand-by disk units are deenergized to be held in the cold condition. Holding the disk units in a cold condition reduces power consumption and prevents any shortening of the disk unit life due to rotation of the disks under an energized condition. Alternatively, the disk units are held in an energized state but the disks of the disk units are not rotated according to commands from channel controllers 8a- 8e in a normal condition. During diagnosis, the disks are rotated, and after the diagnosis, the disks are again stopped from rotating, thereby enabling a longer life. In this case, no special H/W is required for turning ON and OFF the power supply for the disk units. As explained above, according to the present invention , there is provided an array-type recording device having stand-by disk units which replaces faulty disk units if constituent disk units fail, and a maintenance diagnosis means for diagnosing the stand-by disk units periodically or irregularly and for, when any abnormality is detected by the diagnosis, disabling and separating the stand-bys disks from the system. A means for selecting and setting the number of stand-by disk units is further provided. The stand-by disk units may be held in a "hot" condition in which they are always available, in a "cold" condition in which power supply is turned off except during the time of diagnosis and replacement, or in combination of the "hot" and "cold" conditions. The stand-by disks which have been held in a "cold" condition are energized at the time of diagnosis to conduct diagnosis and deenergized after the completion of diagnosis to be held in the "cold" condition. Alternatively, the stand-by disk units which are held in a "cold" condition are held energized but the disks of the disk units are not rotated in a normal state. The disks are rotated during diagnosis and stopped rotation again after completion of the diagnosis. In the array-type recording device illustrated in Fig. 2, maintenance diagnosis processor 20 is adapted to collect error information on constituent disk units during the operation of the system and store the information in error storage means 19 comprising a magnetic disk unit and the like. If any error exceeding a predetermined level occurs in a certain disk unit, the disk unit is predicted to be a possible faulty disk unit, and is replaced with a stand-by disk (by means of a background process or a foreground process), and the possible faulty disk unit is separated from the system. This fact is exhibited on operation display panel 21. Replacement of a disk unit with a stand-by disk is controlled by microprocessor 3 during the operation of the system setting a replacement completion time depending on system performance requirements or a plurality of preferential replacement levels. Such a replacement process may be executed reducing any load imposed on the system by selecting a replacement completion time or anyone of preferential replacement levels. In addition to displaying a system status on operation display panel 21, a replacement process, a separation process and other status may be communicated to a maintenance center (not shown) by remote communicating device 22 as fault information. This arrangement enables quick maintenance such as exchange of separated disk units to be executed, whereby such a problem as shortage of stand-by disks may be prevented. Maintenance diagnosis processor 20 may be substituted for a maintenance diagnosis program performed by microprocessor 3. As explained above, according to the present invention, there is provided an array-type recording device having an error information storage means adapted to collect and store error information on constituent disk units during system operation, and a maintenance diagnosis means adapted to decide that a disk unit in which an error exceeding a predetermined level occurs is a possible faulty disk unit, replace the possible faulty unit whith a stand-by disk unit and separate the possible faulty disk unit from the system. The array-type recording device may further in clude a means for replacing a faulty disk unit with a stand-by disk unit during the operation of the system and a means for setting replacement completion time in accordance with a system requirement or a plurality of preferential replacement process levels. It ist also possible to provide a remote communicating device which is capable of communicating replacement execution information or fault information of the array-type device with a maintenance center.

Claims: A recording device comprising: (a) primary recording units (9a-9e) for recording data; (b) stand-by recording units (11) which are functionally identical to said primary recording units (9a-9e) usable in place of faulty ones of said primary recording units (9a-9e); (c) a maintenance diagnosis means (20) for irregularly or periodically diagnosing in a background operation said stand-by recording units (11) to decide whether any of said stand-by recording units (11) is faulty or not; and (d) a means (20) for selecting and setting the number of said stand-by recording units (11) depending on the reliability of the recording device as a result of periodical or irregular diagnosis of the primary recording units (9a-9e). A recording device as claimed in Claim 1, wherein said stand-by recording units (11) are always held in an available condition, held in a deenergized and disabled condition except for at the time of diagnosis or replacement, or held in a combination of above two conditions. A recording device as claimed in Claim 2, wherein the conditions in which said stand-by recording units (11) are held are selectable. A recording device as claimed in Claim 2, wherein said stand-by recording units (11) in a disabled condition are energized at the time of diagnosis and deenergized after the completion of diagnosis so as to be held in a power-off condition. A recording device as claimed in Claim 2, wherein said stand-by recording units (11) in a disabled condition are kept energized with physical operation of said primary recording unit normally being stopped, and, while diagnosis is executed, said primary recording unit is operated and then is stopped again after the diagnosis is completed. A recording device as claimed in one of Claims 1 to 5, further comprising an error recording means (19) for recording error information during recording data in and reproducing data from said primary recording unit (9a - 9e), wherein said maintenance diagnosis means (20) is operable to decide whether said primary recording unit (9a - 9e) should be replaced with said stand-by recording unit (11) in accordance with the error information recorded in said error recording means (19). A recording device as claimed in Claim 6, wherein said primary recording unit (9a - 9e) may be replaced with said stand-by recording unit (11) during the operation of the system and a time required for the replacement in compliance with a system request or a plurality of preferential replacement levels is set. A recording device as claimed in one of Claims 1 to 7, further comprising a remote communication means (22) whereby information about the replacement or fault information about said recording device may be communicated to an external locations such as a maintenance center.

Inventors: BABA HIROSHI, MATSUMOTO TOSHIO, BABA, HIROSHI, MATSUMOTO, TOSHIO, BABA, HIROSHI, MITSUBISHI DENKI K.K., MATSUMOTO, TOSHIO, MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1992
Main classification: G06F11
IPC codes: G06F11, G11C29, G06F3, G06F12, G06F13