Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
1999-11-23
2002-11-12
Beausoleil, Robert (Department: 2184)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C714S006130, C714S710000
Reexamination Certificate
active
06480971
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to media library apparatus based on a so-called RAID scheme and methods of controlling the media library apparatus. More particularly, the present invention relates to an improved media library apparatus and method of controlling the media library apparatus which can enhance efficiency of data write processing on media by allowing the write processing to continue even after all substitute sectors of the media are used up.
Library apparatus for handling recording media organized in RAID (acronym for “Redundant Array of Inexpensive Disks”) arrays have been known extensively today. In a typical example of such library apparatus, as shown in
FIG. 4
, a plurality of (six in the illustrated example) library units U
1
-U
6
are simultaneously activated in response to data read/write control instructions (e.g., in the form of an electric signal), given from a not-shown higher-order processor such as a personal computer or via a control panel P, so as to carry out data read/write processing while performing a so-called “data striping process” on media inserted in respective drive devices of the library units U
1
-U
6
. Namely, a RAID controller
6
of the library apparatus issues control instructions, in response to which each of the library units U
1
-U
6
uses its holder/transporter to automatically transport a designated medium from one of a multiplicity of storage shelves or cells to the associated drive device. After completion of the media transportion within all the library units U
1
-U
6
, the drive devices are activated in a parallel fashion in order to carry out the data read/write processing while performing the data striping process. The above-mentioned RAID controller
6
, which comprises a microcomputer including a MPU, a ROM, a RAM (all not shown), etc., controls the transportation of the media by the holder/transporters and also controls the data read/write processing by the parallelly-driven drive devices.
In the above-mentioned “data striping process”, each 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 then circulatively delivered to the individual drive devices so that the stripe units are written distributively across the media inserted in the respective drive devices. In both the data read processing and the data write processing during the data striping, a plurality of the media to be processed concurrently are accessed simultaneously while being regarded as a single medium. By thus operating the plurality of drive devices in a parallel or concurrent fashion, the conventional media 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 to date, which are designed to achieve higher reliability by employing redundancy information; 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 sophisticated disk array apparatus employing the redundant information are also commonly called RAID (Redundant Array of Inexpensive Disks) handling apparatus.
The conventionally-known RAID library apparatus are also arranged in such a manner that in case a trouble, i.e., an abnormal condition, such as a malfunction or complete failure (e.g., access error), occurs in any one of the media on which the data read/write processing is being performed concurrently, the data and redundancy information are read out from all the other concurrently-processed media free of trouble and then a predetermined data recovery process is performed, on the basis of the read-out data and redundancy information, to recover the data of the medium where there has occurred the trouble or abnormal condition. In addition, the conventionally-known RAID library apparatus use hard disks as the media, but none of them use non-fixed, transportable media.
Although DVDs (Digital Versatile Disks) have been used more and more popularly as high-density digital recording media in recent years, there has not yet been proposed an efficient RAID library apparatus that uses such DVD media. Further, management of abnormal data etc. in the conventional RAID library apparatus has been made using only one management region.
Disk-shaped recording media, such as the above-mentioned DVDs and optical disks, generally have a plurality of tracks formed concentrically or helically about their rotational axis, and each of these tracks is divided into a predetermined number of “sectors” having an uniform circumpherential length. To write or read data to or from such a medium, access is made to data areas, one by one, partitioned into these sectors. Not all the tracks of the medium are usable by a user; namely, the data areas usable by the user (i.e., user data areas) are limited. Other tracks than the user data areas are used as a “substitute sector” (or spare sector) and the like; typically, the substitute sector is for usable as a substitute for a regular sector having been found to be defective in the user data areas. More specifically, the substitute sector on the medium is a data area limitedly allocated in advance and typically having a capacity of one or more regular sectors. Note that such a substitute sector, in general, is used only in a medium where a decificient regular sector has been found, independently of RAID processing.
When some trouble (i.e., defect) has been detected in one of the regular sectors of any one of the media during the data write processing, the data is written into the substitute sector in place of the defective sector. However, in a situation where other data have already been written in the entire area of the substitute sector of the medium, i.e., where there is no empty or unused area left in the substitute sector of the medium, the data write processing can not be performed at all any longer even though one or more other data areas in the medium are still empty.
Namely, the conventionally-known RAID library apparatus would present the problem that they can not be used as RAID handling apparatus unless there is an empty area in the substitute sector in every one of the media on which the data write processing is to be performed. For example, once any one of the media has run out of empty area in the substitute sector during the data write processing, the RAID library apparatus would undesirably halt or suspend the write processing even though the data write processing has not yet been completed. In such a case, there arises a need to replace the medium, having run out of empty area in its substitute sector, with a new one and then restart the data write processing from the beginning. Thus, an enormous amount of time has to be spent in completing the data write processing and no other operations can not be performed at all during all these processing, which would result in a very poor overall processing efficiency of the library apparatus.
Further, with the conventionally-known RAID library apparatus, it was not possible f or the user to know, prior to the data write processing, a size of empty areas present in the substitute sector. Therefore, it was not possible to readily predict when the substitute sector would be used up during the course of the data write processing.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a media library apparatus and method of controlling the media library apparatus which achieve reliable management of data indicative of trouble , defects or the like of the media and which also achieve an enhanced efficiency of data write processing on the media by allowing the data write pro
Matsumoto Tadashi
Suzuki Hiroyuki
Beausoleil Robert
Chu Gabriel
Hitachi Electronics Engineering Co. Ltd.
Morrison & Foerster
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