Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data verification
Reexamination Certificate
1998-09-17
2001-03-13
Kim, W. Chris (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data verification
C360S048000
Reexamination Certificate
active
06201655
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to data formatting in a storage device, and in particular to a magnetic disk storage device of an ID less (or ID Few) system, and further to a procedure using spare sectors to replace bad sectors in a magnetic disk storage device.
BACKGROUND OF THE INVENTION
A conventional magnetic disk storage device has a system in which ID information is provided for storing position information and replacement information for each sector. In a Read/Write process, the sectors that are already replaced are skipped by referring to the ID information. In this procedure, as mentioned in unexamined patent publication JP 05-282794 (Japan), for example, the information of how many sectors the true sector has slipped due to bad sectors is supervised in the ID information, and it is required that the true target sector be re-accessed after reading the ID information by using the physical address which is converted from a logical address. In this case, if many slipped sectors exist, there exists a high probability that the target might be slipped to the next track. Therefore, spare sectors are supervised in units of a track or cylinder. If the spare sectors were supervised in expanded zone units (a unit having a spare sector is called a zone), the performance would deteriorate due to the requirement of reissuing the seek command.
In another example of the prior art, used in a SCSI interface, a mode sense command is provided to verify a spare region unit from an upper host computer. Since a unit of a spare region is less than one track in the case of track/cylinder zone replacement, a bad track is replaced (jumped) to a dedicated track in the replacement of the bad track.
SUMMARY OF THE INVENTION
The conventional technology has a problem that the format efficiency (the ratio of data area a user can actually use to the total data area: effective storage capacity) deteriorates because more spare sectors are required than the average number of bad sectors that exist in a whole drive, since the drive requires spare sectors for every track or cylinder.
Further the conventional technology has a problem that performance severely deteriorates due to additional seek (requiring additional disk rotation), and if bad sectors concentrate in a certain zone, a “skip sector” replacing procedure in which the sector is skipped to another zone is required, or a replacement of the concerned track as a bad track is required.
Moreover, the conventional technology has a problem that performance and format efficiency deteriorate due to the use of a “skip track” replacing procedure in which the bad track is jumped to a dedicated alternative track.
An object of the invention is to offer a replacement procedure using a “slip sector” method which secures data continuity, by preparing a spare region in a magnetic disk storage device per notch, which has a different capacity than that of a track, or per volume, and slipping all of the bad sectors at the formatting. This reduces the size of the spare region required for sector replacement or track replacement.
Another object of the invention is to reduce the memory capacity requirements and to prevent substantial increase in processing time due to searching for a bad sector list, although the list is required to be resident in the memory.
The purpose mentioned above is accomplished by supervising the locations of a “slip sector, a “skip sector”, a “slip track”, and a “skip track” in a map through preparation of a spare region for each notch (or per disk unit volume) and by sharing the spare region. The number of sectors the target sector has been slipped is counted by a defect list (bad sector list) after replacement has been executed. In the formatting of the storage device, all of the bad sectors are made into slip sectors by utilizing the spare region.
Further, a “slip track” method is used in which valid tracks are slipped in order, to avoid excessive seek or excessive rotational latency when a bad track is detected, because a spare region for several tracks is secured owing to the expansion of the unit in which the spare region is provided.
Another object of the invention is accomplished by providing a two stage table for the defect sector list that is stored in memory. The two stage table has a first stage table that stores a pointer using a unit of the upper address (cylinder address, for example) that points to the lower address of the defective sector entry in the list that is stored or supervised in the second stage table.
Thus, an increase in searching time is prevented by searching only the table in the first stage of the two stage table which supervises the upper address, and by identifying the target track by counting the number of slipped sectors due to bad sectors in front of the concerned address (cylinder for example).
REFERENCES:
patent: 5357381 (1994-10-01), Yasuda et al.
patent: 5450251 (1995-09-01), Kitagawa
patent: 5822142 (1998-10-01), Hicken
patent: 5995308 (1999-11-01), Assouad et al.
patent: 6025966 (2000-02-01), Nemazie et al.
patent: 5-282794 (1993-10-01), None
Hirose Tsuneo
Mizuno Yusuke
Takayasu Atsushi
Watanabe Mitsunobu
Yamane Yuji
Hitachi , Ltd.
Kim W. Chris
Mattingly Stanger & Malur, P.C.
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