Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1998-12-28
2001-06-19
Nguyen, Than (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C365S185330, C365S230030, C711S101000, C711S102000, C711S104000
Reexamination Certificate
active
06249838
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the storage of information relating to a physical data storage medium indicative of its usage or design lifetime such that at least some of the information remains coupled to the medium such as storing, in a flash memory header, information relating to the number of flash memory erasures.
BACKGROUND OF THE INVENTION
A number of information storage media have a predeterminable or calculable design lifetime or maximum usage. An example is flash memory which typically can support a number of memory erasure operations (such as in the range of about 10
4
through about 10
5
erasures) but which can be expected to fail some time after that number of erasures. Accordingly, the expected design lifetime of a flash memory is more a function of the manner in which it is used (and particularly, its erasure frequency) than the mere passage of time. To achieve a degree of confidence in the continued operation of a system which includes flash memory, the flash memory should be replaced as the number of erasure operations performed using the flash memory approaches the expected design lifetime of the flash memory. Accordingly, it would be useful to provide a system in which replacement of the flash memory (or similar data storage medium) will be encouraged, requested, and/or required at an appropriate time.
Although it would be possible to provide a system for manually providing a reminder of the need for a media replacement (such as marking reminder on a calendar) there is a significant risk that this type of reminder would become unassociated with the data storage medium. For example, if the data storage medium is a medium which is a removable medium (moved from one computer or other device to another computer or other device, a manual calendar reminder, for example, may not properly reflect the appropriate replacement date for the particular medium which is currently inserted in a computer (or other device). Furthermore, a manual reminder such as a calendar entry may be infeasible when design lifetime is based, not on date of installation, but on information that may not be readily available for, e.g., manual entry on a calendar, such as date of manufacture of the medium. Furthermore, when design lifetime is determined or affected by factors other than mere passage of time (such as number of erasures or similar usage factors) tracking such use dependent factors can be burdensome or infeasible for a manual reminder system. Accordingly, it would be useful to provide a system in which accurate and current design lifetime information, based on appropriate criteria, remain coupled, preferably physically coupled, to the memory medium or device.
Although, in a number of computing contexts, it may be possible to configure a computer to provide, or assist in providing, appropriate media replacement reminders, it can be disadvantageous to impose additional computing burden or “overhead” on a CPU (Central Processing Unit) for tracking usage of each storage medium and it can be burdensome to impose a programming or data entry burden on programmers or users. Accordingly, it would be useful to provide a system for encouraging or assuring appropriate storage medium replacement without substantially incurring or increasing computing, programming or data entry burden.
The type of response which is most appropriate, as the end-of-design-lifetime approaches, will vary depending on such factors as the type of medium involved and type of computing system or computing network where the device is employed and/or user preferences. In especially critical computing environments, it may be undesirable to give a user an opportunity to ignore or override a warning or request that media replacement is due. Accordingly, it would be useful to provide a system in which the system can be configured so as to respond in different fashions to the detection of an approaching end-of-design-lifetime event.
SUMMARY OF THE INVENTION
The present invention provides for storing, and, as appropriate, updating or incrementing system or component information, such as remaining-expected-lifetime information, (or information from which remaining-expected-lifetime information can be determined or derived) (REL), in a fashion which remains associated with a data storage medium, and, in response, providing an appropriate output, warning or action. In various embodiments, the REL information may be stored using the same storage medium that is used for storing the data for which the data storage unit is intended (“main storage medium”), e.g., in the header portion or other portion of the memory array of a flash memory, nonvolatile random access memory (RAM) or other RAM, a header portion of disk storage in a fixed or hard disk drive (HDD) and the like. Alternatively, the REL information can be stored on a separate storage device such as providing an HDD storage unit with a small flash memory or other memory mounted on or otherwise coupled to the HDD unit. In either case, the memory device (or a portion of memory medium) used for storing at least a portion of the REL information is physically mounted on or otherwise physically coupled to the data storage unit to which the REL relates. In this context, a data storage unit to which the REL information relates is the unit which would normally be replaced at the end of the expected lifetime indicated by the REL information. For example, in the case of a flash memory device, the entire flash memory device would normally be replaced at the end of the expected lifetime of the flash memory. In contrast, a removable medium hard disk drive (RMHDD) may have an expected lifetime for the removable medium which is different from the expected lifetime of the drive mechanism. In this situation, if REL information relating to the removable medium is provided, preferably at least some of such REL information is stored in a device which stays with the removable medium when the medium is removed from the drive (e.g., so that even if the removable medium is inserted in a different drive, it is still possible to detect the appropriate remaining-expected-lifetime and to take the appropriate action. If REL information is provided in connection with the drive device for the RMHDD, it would generally be preferred to store at least a portion of the REL information related to the drive portion on the drive itself, (as opposed to on the removable medium) so that even if new removable media were inserted in the RMHDD, the appropriate REL information related to the RMHDD drive portion would be available. Furthermore, in this situation, if the drive portion of the RMHDD was replaced at the end of the expected lifetime of the drive portion, the replacement RMHDD would preferably contain REL information related to the replacement RMHDD. In this way the REL information is stored in a fashion such that the REL information moves with the data storage unit to which it relates, regardless of replacement of parts or media in the overall system.
The REL information can be used in a number of fashions. In one configuration, the CPU or similar central computing device can periodically read the REL information (in a “polling” fashion). Alternatively, the data storage unit can include logic which periodically or continuously monitors the REL information and sends an interrupt signal to the CPU when the remaining expected lifetime approaches (is within a relatively small distance from) an indication of zero remaining lifetime. The REL information stored on the data storage unit may be sufficient, in itself, to determine remaining expected lifetime (such as a counter in a flash memory holding the remaining expected available erasures) or may be information which is combined with information stored elsewhere in order to calculate, look up or otherwise determine remaining expected lifetime (such as a serial number or other identifier number stored in the data storage unit which is used to index into a data base of REL information stored elsewhere. In any case, once it is determined that
Cisco Technology Inc.
Nguyen Than
Sheridan & Ross P.C.
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