Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1999-10-15
2002-04-02
Yoo, Do Hyun (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C369S030050, C714S006130
Reexamination Certificate
active
06366982
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to handling and management of RAID-organized recording media in library apparatus, and more particularly to a technique of simplifying and automatizing the handling and management of recording media as subjects of a data striping process.
Library apparatus for handling transportable recording media organized in RAID (acronym for “Redundant Array of Inexpensive Disks”) arrays have been known, a typical example of which includes a holder/transporter for holding and transporting a designated recording medium such as an optical disk (hereinafter simply referred to as a “medium”) to a designated place in the library apparatus, a plurality of storage columns having a multiplicity of storage shelves or cells for storing a multiplicity of media, and a plurality of drive devices for writing or reading data to or from a medium inserted therein. The library apparatus also includes a RAID controller for executing a so-called “data striping process” on the media inserted in the plurality of drive devices in a parallel or concurrent fashion. Such library apparatus for RAID-organized media are, so to speak, disk array apparatus where, for each of the storage columns, a designated medium is automatically transported via the holder/transporter between one of the storage shelves and the drive device and where the respective drive devices associated with the individual storage columns are operated in a parallel fashion to perform the data read/write operation on the media inserted therein while executing the data striping process on the inserted media. The above-mentioned RAID controller, which comprises a microcomputer containing a MPU, a ROM, a RAM, etc., controls the transportation of the media by the holder/transporter and also controls the parallel data read/write operations by the drive devices.
In the above-mentioned “data striping process”, one complete data is broken down into a plurality of lower-order units called “stripe units” each having a predetermined data size such as a bit, byte or predetermined data block, and the thus-obtained stripe units are circulatively delivered to the individual drive devices so that the stripe units are written distributively across a plurality of the media inserted in the drive devices. The data striping process is also performed such that the stripe units are read out from the media, already having undergone the data write operation, so that the read-out stripe units read out from the individual media can be rebuilt together for use as one complete data. In both the data read operation and the data write operation during the data striping process, a plurality of the media to be processed concurrently are regarded as a single medium and therefore accessed simultaneously. By thus operating the plurality of drive devices in a parallel or concurrent fashion, the conventional library apparatus have been attempting to substantially increase a data transmission speed in accessing a large quantity of data. However, reliability of the library apparatus would unavoidably deteriorate as the number of the drive devices to be operated in parallel increases. Thus, more sophisticated disk array apparatus have been proposed, which are intended for achieving higher reliability by employing an information redundancy scheme; for example, duplicate copying of data in the case of RAID level
1
, data redundancy by Hamming code in the case of RAID level
2
, or data redundancy by parity in the case of RAID level
3
. Such disk array apparatus are also called RAID (Redundant Array of Inexpensive Disks) library apparatus.
The known RAID library apparatus are arranged in such a manner that in case a trouble, i.e., an abnormal condition or anomaly such as a malfunction or complete failure, occurs in any one of the media on which the data read/write operation is being performed concurrently, the data and redundancy information are read out from all the other concurrently-processed media and a predetermined data recovery process is performed, on the basis of the read-out data and redundancy information, to recover the data of that medium having got into the abnormal condition.
Although DVDs (Digital Versatile Disks) have been getting more and more popular as high-density digital recording media in recent years, there has not yet been proposed an efficient RAID library apparatus for handling DVD media.
As stated above, the conventional RAID library apparatus perform the data striping process to break down one data into a plurality of stripe units for distributed storage across a plurality of media. Typically, the media to be simultaneously subjected to the data striping process are either randomly selected by a human operator outside the apparatus via a keyboard or other input device or automatically selected by a computer program or the like prestored in a ROM or RAM of the RAID controller. Various pieces of information pertaining to the media simultaneously subjected to the same data striping process, such as information as to in which of the storage shelves the media are being stored, are written into the RAM or the like. Specifically, in the conventional RAID library apparatus, each of the storage shelves has imparted thereto a different or unique physical address as information indicative of the location, in the library apparatus, of that storage shelf. As a consequence, the total amount of the media-pertaining information written in the RAM or the like tends to become enormous, which would significantly complicate management (i.e, address management) of the information pertaining to the media subjected to the data striping process.
Further, in the case where some abnormal condition (malfunctioning or complete failure) has occurred in one of the media during the data striping process, it has been conventional to replace the abnormal medium with a normal medium by manual labor. Also, in order to recover the data written on the abnormal medium, it is necessary to read out the data and redundancy information from one of the normal media having been subjected to the same data striping process as the abnormal medium. To this end, it has been customary to manually take out a necessary substitute medium from one of the storage shelves and insert the taken-out substitute medium into the associated drive device. However, because the information (address) of the storage shelf storing the substitute medium can be acquired only while the library apparatus is turned on or actually in operation, it was not possible to readily obtain such a substitute medium. As understood from the foregoing, the conventional RAID library apparatus achieve a very poor operating efficiency in that once an abnormal condition occurs in one of the media during the data striping process, a great amount of time must be consumed in recovering the data of the abnormal medium and no other processing is permitted until the necessary data recovery is completed. Besides, because the abnormal and normal media can not be distinguished from each other by their appearances, the manual replacement of the abnormal medium with the normal or substitute medium tends to be done erroneously.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a RAID library apparatus and a method of controlling the RAID library apparatus which achieve a greatly enhanced operating efficiency by simplifying management of media and automatizing replacement of an abnormal medium with a normal medium.
It is another object of the present invention to provide a RAID library apparatus and a method of controlling the RAID library apparatus which allow an abnormal medium to be automatically replaced with a normal medium without a human intervention, to thereby avoid an erroneous interchange between the media.
In order to accomplish the above-mentioned objects, the present invention provides an improved media library apparatus which comprises: a transportation mechanism for transporting a transportable medium; a plurality of storage columns having a mul
Matsumoto Tadashi
Sasaki Mikio
Suzuki Hiroyuki
Hitachi Electronics Engineering Co. Ltd.
Moazzami Nasser
Morrison & Foerster / LLP
Yoo Do Hyun
LandOfFree
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