Patent Application
20060291084
Some electronic systems include a storage drive that can store data on a removable storage medium. Because the storage medium is removable, the data on the storage medium can be written by one or more storage drives. Further, one or more portions (e.g., sectors) of a storage medium may malfunction. The malfunction may be caused by the storage medium itself or by a drive while accessing the storage medium. Having information by which such malfunctions may be diagnosed would be desirable.
For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings in which:
Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, computer companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. The verb “record” means to store, write, or otherwise transfer data onto a storage medium. The term “system” refers to a collection of two or more components and may be used, for example, to refer to a computer system or a subsystem of a computer (e.g., a storage drive).
The storage drive 30 is adapted to receive a removable storage medium 32 as may be inserted by a person or by a machine (e.g., an automated, tape drive loading system). The storage medium 32 may comprise any suitable type of medium such as an optical disk, a magnetic disk, solid state memory, etc. Further, the storage medium may be implemented as a “write-once” medium or a “re-writeable” storage medium. Data can be recorded onto a write-once medium more than once, but once data is written to a write-once medium (e.g., CD-R), such data cannot be overwritten or erased. Data on a re-writeable storage medium can be overwritten or erased.
The storage drive 30 may also include a CPU 36 and code 38 that can be executed by the CPU 36. One or more of the acts described herein may be performed by the storage drive's CPU 36 executing the code 38. Moreover, all of the acts described herein may be performed by the code 38 or by the device driver 26. In other embodiments, some of the acts described herein may be performed by the device driver 26 while other acts are performed by the code 38. The following discussion refers to the code 38 performing various actions, but in other embodiments device driver 26 may additionally or alternatively be used.
The storage drive 30 also comprises an identifying value such as a drive identifier (“ID”) 34 that may uniquely identify the associated drive apart from all other drives. For example, the drive ID may comprise a serial number assigned by the drive manufacturer. In other embodiments, the drive ID 34 may be unique to at least some, but not all, other drives. It is generally sufficient for purposes of the subject matter disclosed herein that the drive ID 34 is such that there is a sufficiently low probability that the same storage medium 32 may be used in two or more drives having the same drive ID. The term “unique” (as in “unique” drive ID) is used in both contexts in this disclosure. The drive ID 34 may be stored in non-volatile memory in the storage drive 30 or may be hard-coded into the drive's circuitry (e.g., in unique patterns on traces formed on a printed circuit board contained in the drive). In some embodiments, the drive ID is permanent and thus not alterable. It is also suitable for the drive ID to be permanent, or at least difficult to alter without specialized equipment or processes. In other embodiments, the drive ID comprises an identifier of the host 22 instead of, or in addition to, an identifier of the drive. Further still, the drive ID comprises publicly available information pertaining to the system 10 or a user of system 10. The drive ID may additionally or alternatively contain private information that is lawfully retrievable pursuant to a valid legal process (e.g., a search warrant) to protect the privacy of a user of the system 10.
The drive ID 34 may comprise a value containing alphanumeric characters and/or other symbols. In at least one embodiment, the drive ID 34 comprises a 64-bit value comprising a manufacturer code (16 bits), a model code (16 bits) and a serial number (32 bits). Each different storage drive manufacturer may be assigned a unique manufacturer code and with 16 bits, there are more than 65,000 different manufacturer codes possible. Each different model, including revisions if desired, of a storage device may also be assigned a unique model code. With 16 bits used for the model code, there are more than 65,000 uniquely available model codes. The serial number generally is unique to each drive. As such, two drives of the same model and provided by the same manufacturer will still have different drive IDs because the serial number component of the drive IDs will differ. The three components of the drive ID (manufacturer code, model code, and serial number) may be concatenated together or otherwise combined or used together in any suitable manner.
In an alternative embodiment, every drive of a particular model may have the drive ID encoded in firmware running in the drives. In this embodiment, each drive of a particular model has the same 32-bit serial number. If the firmware is upgraded, the drive serial number is not changed and is still available. In accordance with another embodiment, the drive ID is generated by the host (e.g., by the CPU 24 in accordance with the device driver 26). When the drive is installed, the driver may prompt the operator for a number, which might, for example, be a human-readable serial number printed on the drive but not readable by the drive controller electronics. Alternatively, just the manufacturer number and model number could be manually entered and the device driver 26 could generate a random 32-bit serial number. Alternatively, the device driver could generate a serial number from a unique number associated with the host computer, such as a serial number of the firmware (e.g., BIOS) for the host. If the device driver provides the serial number, either the device driver should save the number in non-volatile memory, or the device driver should employ a deterministic algorithm to always recreate the same number every time the driver is loaded. If the device driver provides the serial number, the drive may obtain the drive identification from the device driver at initialization time.
In general, recorded data is formatted into addressable units that may be referred to in a variety of ways. Examples include sectors, blocks, clusters, tracks, and groups of other units such as an error correction code (“ECC”) block which contains a predefined number of sectors. In the following discussion, the term “addressable unit” is used to generically refer to any of the units of storage listed above or other known units of storage.
In accordance with various embodiments of the invention, each time an addressable unit of the storage medium 32 is written with data by a storage drive 30, the storage drive's CPU 36, under control of code 38, also writes an index value into the addressable unit being written with data. The index value written into the addressable unit of the storage medium 32 corresponds to the particular storage drive 30 that is performing the write operation. The index value written to the addressable unit corresponds to the ID of the drive as reflected by way of the drive ID table 56. For example, if drive 1 writes an addressable unit of the storage medium, then, in addition to the data, drive 1 also writes its corresponding index value into the addressable unit. Moreover, each addressable unit of storage medium 32 in which data is written is also written with an index value that identifies the particular storage drive 30 that was used to write the addressable unit.
It may happen that all of the entries in the drive ID table 56 are written with drive IDs and, if implemented in the table, index values. When this happens and in accordance with at least some embodiments, a new storage drive that attempts to write data to an addressable unit (i.e., a drive whose drive ID is not already stored in table 56) may cause a reserved value such as 00h or FFh to be written to the addressable unit(s) instead of the drive ID. In other embodiments, once the table 56 becomes full, the drive IDs in the table can be erased by way of a user-initiated maintenance procedure. An offset value can then be stored as part of the table or elsewhere on the storage medium. This offset value represents the number of entries in the table 56 and is used to compute new indices for additional drives. For example, if the table 56 has 32 entries and all 32 entries are occupied with drive IDs (i.e., 32 drive IDs of 32 different drives), all 32 drive IDs can be erased from the table. In this example, the offset value will be 32. When a drive subsequently attempts to write to an addressable unit, that new drive, being the first drive to write the storage medium following the erasure of the table 56, will be assigned an index value of 33 which is computed by adding an initial index value of 1 to the offset value of 32. Similarly, the next drive to write the storage medium will be assigned an index value of 33, and so on. The index values actually stored in the table 56 will be 1, 2, 3, etc., but are added to the offset value 32 when the table 56 is accessed.
In accordance with the embodiments described above, index values are stored in the addressable units as the identifying values by which to identify the drives writing the addressable units. The table 56 can be used to identify the particular drive that wrote an addressable unit given the associated index value. In some embodiments, the index value associated with a particular drive is stored in table 56 as shown in
In some embodiments (e.g., legacy drives), a drive identifying value may not be available and a predetermined value (e.g., 00h) is stored in the addressable unit of the medium. Also, it may be that all possible drive identifiers (e.g., index values) are already in use and thus none are available for a new drive. In this case, a predetermined value is used to store in the addressable unit of the medium in place of a drive-identifying index value.
The embodiments described above result in storage media that contain audit information that can be used to identify which drives wrote specific addressable units of the storage media. This audit information can be used in a variety of ways. For example, if an addressable unit of a storage medium 32 is determined to be defective and the index value written to that addressable unit can be determined, then, by examining the drive ID table, a determination can be made as to which drive last wrote to that particular addressable unit. The defect to the addressable unit may be caused by a problem with a particular storage device that can uniquely be identified by information in the addressable unit(s) written by the storage device and the medium's drive ID table. Accordingly, in some embodiments, a method may be performed by a computer system having a processor and executing software suitable to implement the method. The method so performed comprises retrieving information from the removable storage medium 32 and, based on the information, determining which of a plurality of storage drives was used to store the data on the removable storage medium. Specifically, the computer system receives the removable storage medium and the computer system's software is executed to perform the method to determine which one or more storage drives previously wrote data to the removable storage medium. The act of retrieving the information explained above comprises retrieving a table 56 from the removable storage medium. The act of retrieving the information also comprises retrieving any index values stored in the addressable units of the removable storage medium that have previously been written with data. The method further entails examining the table 56 and determining if any index value(s) read from any of the addressable units on the storage medium contain matches to any index values contained in the table. The drive IDs stored in the table provide a mechanism by which the identity can be ascertained of any drive that has previously written data to an addressable unit of the storage medium and whose index value is stored at such addressable unit.
Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, the teachings provided herein are applicable to computer systems as well as standalone storage devices such as optical disc video recorders.
