HK1008608B - Spare and calibration sector management for optical worm media - Google Patents

Description

Spare sector and calibration sector management for write-once read-many optical discs

Technical Field

The present invention relates to optical storage devices, and in particular to the management of spare and calibration sectors in write-once optical storage systems.

Background

When recording information on an optical disc, the laser light should be fixed at a power level at which recording marks can be appropriately formed, whether these marks are represented by variations in reflected polarization of a spot on a rewritable magneto-optical (MO) disc, by grooves ablated on the surface of a write-once ablated disc, or by variations in reflectivity between crystalline and amorphous areas of a phase-change (PC) disc. However, even if the laser power is fixed when producing the optical disc, there may be many factors that make this fixation method not optimal. For example, two pieces of media from different manufacturers, or different batches from the same manufacturer, may have slightly different properties and therefore slightly different responses when used with the same laser power tool. Other factors that affect the optimum laser power level include: drive and media life, drive operating temperature, media temperature and temperature differential between the media and the drive, media contamination level, laser spot size variation, and focus and tracking sensor offset.

Therefore, a technique for performing driver self-correction when using a driver has been proposed. In a system employing the above technique, correction patterns (which cannot be confused with user data) are recorded at mutually different laser power levels on one or more sectors. The sector is then read back and the optimum laser power level is selected for recording based on parameters such as read back signal amplitude, mark (mark) edge jitter, mark peak pulse position, mark space asymmetry and mark length. The correction is performed at predetermined intervals each time the drive is powered on, wherein the correction is also performed each time the verification fails. When correction is performed on an MO optical disc (or other rewritable medium), it is possible to erase a sector previously used for correction and reuse the sector. Thus, only a few such sectors are required. Conversely, when correction is performed on a Write Once Read Many (WORM) disc, sectors previously used for correction cannot be reused. Therefore, when the optical disc is a new optical disc, it is necessary to have many calibration sectors.

Recently recommended WORM media of 1.3GB per side 130mm require a significant number of correction sectors, especially compared to currently common WORM media of 325MB per side 130mm, which employs Peak Pulse Modulation (PPM) recording techniques, and Pulse Width Modulation (PWM) recording techniques. The recording capacity is increased by 4 times due to mainly increased recording density, reduced mark size and the adoption of the PWM recording technique. Because transform coding information is used, PWM requires greater precision in mark interval writing. Furthermore, PWM uses marks of different lengths, which in turn require additional quality mark structures. All these factors increase the necessity to use the optimum write power to constitute a quality mark with precisely located edges. In fact, in certain operating environments, the drive must be calibrated each time the disc is installed in order to achieve the required data reliability and performance. It will be appreciated that if all calibration sectors are used, no further information can be recorded on the disc, since no capability is available to ensure an appropriate laser write power level.

During verification, when a recorded data sector is confirmed to be defective, the data must be written to other sectors. In some WORM media's disc format configuration, one or more sectors of the disc are set aside as spare sectors to replace "primary" defective sectors. However, if the spare sector is used up, other data cannot be reliably recorded.

European patent application 0577214 a2 discloses a record carrier having a plurality of extents divided into sectors. An integer number of tracks is included in each divided sector area. In the record carrier disclosed in this application the writing density is controlled using the space. The space is part of the header section and thus part of the sector.

European patent application 0442566 a1 discloses an information recording device in which the laser write power is adjusted by writing a write power correction pattern to a correction area of the record carrier. The pattern is then read out and the required write power is determined. While european patent application 0555065 a2 discloses the use of spare sectors in the area of the record carrier for correcting the laser beam. All of these patent applications do not disclose the use of correction sectors for each zone in a multi-zone record carrier.

Disclosure of Invention

In view of the foregoing, it is an object of the present invention to provide one or more areas on WORM media and to allocate them to correction and spare sectors.

It is another object of the present invention to provide an initialization process for a WORM media to allocate areas on the media to spare and correction sectors.

It is a further object of the present invention to provide an optical storage apparatus for recording data on WORM media with improved correction sector and spare sector management.

The present invention provides an apparatus and method for efficiently managing calibration sectors and spare sectors on a write-once optical disc that has been divided into extents. Each zone on the optical disc includes a user data area and a reserved area. The sectors in the reserved area may be used as spare sectors (instead of defective sectors in the user area) or as correction sectors (used when correcting the laser write power level). In one embodiment, spare and calibration sectors are not pre-allocated to specific isolated sectors within the reserved area. More precisely, sectors starting from one end of the reserved area are used for spare, while sectors starting from the other end are used for correction. In addition, to avoid potential seek difficulties, the spare sectors are preferably started from the lowest address of the reserved area, and the calibration sectors are preferably started from the highest address of the reserved area.

Upon initialization of the medium, the number of sectors allocated to each reserved area is determined. For example, a media vendor initializing the media prior to distribution makes it impossible for a user to adjust the above allocation. When selling optical discs in an uninitialized manner, the user can select the relative length of the reserved area, or select multiple lengths, to adapt the medium to a particular environment and management mode.

In another embodiment, a general overflow reserve is provided that is used when all sectors in one or more primary reserves associated with all extents are exhausted.

Each sector on the WORM disc contains a DMP (fault management pointer) area, which is recorded when the sector is used. When recording a sector in the user data area of the disc area, writing the address of the sector into a first word of the MDP, and writing the initial address of a reserved area serving the disc area into a second word; and the laser power level of the sector is written into the third word. When the sector in the reserved area of the using disc area replaces the fault sector, writing the address of the spare sector into a first word of the DMP, and writing the address of the fault sector into a second word; and the laser power level used for writing the spare sector is written into the third word. When one sector in the reserved area is used as a correction sector, a write power correction pattern is written into the first and second words, and the optimum power level determined by the correction process is written into the third word.

Also, a method of calibrating a drive during a multi-sector write operation is provided. The first sector is recorded to the user data area of the particular extent and verified. If the verification is successful, recording the remaining sectors to the user data area. However, if the verification indicates that the laser write power is improperly set, a correction is made. Then, at the new correction power level, the first sector is re-recorded to the spare sector in the reserved area, and the remaining sectors are recorded to the user data area.

The foregoing features and other advantages of the invention will be apparent from the following detailed description of the preferred embodiments of the invention, as illustrated in the accompanying drawings.

Drawings

FIG. 1 is a block diagram of an optical storage apparatus of the present invention;

fig. 2 and 3 are simplified diagrams of respective portions of a write-once optical disc of the present invention;

FIG. 4A is a simplified diagram of a radial portion of a write-once optical disc;

fig. 4B is an enlarged view of a partial disc region of the write-once optical disc.

Detailed Description

Fig. 1 is a block diagram of an optical storage device of a drive 2, wherein the invention can be applied with the drive 2. The drive 2 may be a write-once device or a multifunction device (capable of recording WORM media, as well as rewritable media). For the sake of clarity, fig. 1 omits a number of components of the driver 2 (including components only relevant for rewritable operation), which will not be discussed below.

The optical write-once disc 10 may be mounted on a spindle 14 for rotation by a spindle motor 16 under the control of a spindle controller 18. The figure does not show the loading mechanism by which the optical disc 10 is loaded into the drive 2 and down onto the spindle 14; after the disc operation is completed, the loading mechanism reverses the above process and ejects the disc from the drive 2. The head arm carriage 20 is radially movable with respect to the disc 10, the carriage 20 being provided with an objective lens 22, the objective lens 22 being used for accessing all data on a large number of addressable tracks on the disc 10. A coarse adjuster 24 controls the radial movement of the carrier 20.

A light beam (indicated by dashed line 26) from a laser 28 is directed to an optical signal processing section 30 comprising a plurality of optical and electro-optical components 32, which components 32 direct the light beam 26 through the objective lens 22 to the surface of the optical disc 10. The laser controller 34 controls the laser 28; focusing and tracking is performed by a fine adjustment actuator 36, and a focus and tracking circuit 38 controls the fine adjustment actuator 36 using inputs from a relative position focus sensor 40.

The drive 2 is interconnected with a host device 44 via an input/output interface 42. The host device 44 transmits data to be recorded on the optical disc 10 to the data channel 46 via the input/output interface 42. Data read from the optical disc 10, after being converted into an electrical signal, is transmitted to the host device 44 via the input/output interface 42 through the data channel 46. A microprocessor 48 is interconnected with and manages the operation of the components of the drive 2, wherein the microprocessor 48 includes a memory 50 or is interconnected with a memory 50.

FIG. 2 is a simplified diagram of a WORM optical disc 10, the optical disc 10 having been formatted in accordance with the present invention. The area extending radially from the Inner Diameter (ID)102 toward the Outer Diameter (OD)104 is a control region that includes a Phase Encoding Portion (PEP)106, a Standard Format Portion (SFP)108, and a manufacturer region (MFG) 110. A backup (not shown) of the SFP and MFG is located at the OD 104. The optical disc 10 has a single spiral track (track) that extends between the ID 102 and the OD 104 (and may also extend in the opposite direction) and is divided into a plurality of radial extents 112 and 117 (or only one extent) where each extent has a plurality of addressable tracks, each track having a plurality of sectors. Ellipses 114 represent multiple extents between extent 113 and extent 115. In the recommended 4X WORM format, the optical disc 10 has 34 extents and is numbered from outer (extent 0) to inner (extent 33); likewise, the addressing of tracks and sectors is from the outside to the inside. However, the above configuration is merely exemplary and does not limit the present invention.

FIG. 3 is a simplified diagram of a portion of an exemplary extent 113, the extent 113 having a plurality of sectors, only a few of which are illustrated (shown as sectors 130-136, sectors 140, and ellipses 138). An exemplary sector, such as sector 140, includes a header area 144 and user data 142, where the user data has a fault management pointer (DMP) 146. The sectors in the extent 113 are divided into a user data area 160 and a reserved area 170. The number of sectors per extent is determined at the time of manufacturing the optical disc 10, and the number of sectors thereof is gradually increased from the inner extent to the outer extent. However, as described below, in one embodiment, when initializing the disc, a user may determine the ratio of reserved sectors to user sectors in each extent on the disc, and thus the starting address of each reserved area 170. On the other hand, the optical disc manufacturer may fix the ratio of reserved sectors to user sectors so that the user cannot configure the ratio.

In the user area 160, the DMP 146 of a sector (such as the sector 140) includes 3 words, each of which is 4-bytes, and the 3 words are recorded during a write operation. The first word includes the address of sector 140. The second word includes the starting address of the reserved area 170 as a general pointer to the reserved area 170 that does not point to a specific sector in the reserved area 170. The third word includes the laser power value used to write sector 140.

The sectors in the reserved area 170, such as sector 130, also have a DMP area, the contents of which will be described below depending on whether the sector is used as a spare sector or a calibration sector.

During a write operation, when data is recorded on the sector 140, 3 words are recorded on the DMP 146. If the readability of sector 140 cannot be verified, the data is recorded in an unused sector, such as sector 132 in reserved area 170 (hereinafter referred to as a spare sector). The laser beam 26 scans the reserved area 170 for the next available free sector to determine the spare sector. While recording data, the address of the spare sector 132 is recorded in the first word of the DMP of the spare sector 132, and the address of the replaced defective sector 140 is recorded in the second word. The laser power level is recorded into the third word.

When the microprocessor 48 determines that the laser write power needs to be corrected based on a predetermined criterion, such as the number of sectors that cannot be verified, the microprocessor 48 in the drive 2 directs the laser beam 26 to an unused sector, such as the sector 130 of the reserved area 170 (hereinafter referred to as the correction sector). The laser beam 26 scans the reserved area 170 for the next available free sector to determine the calibration sector. A pattern of marks is recorded into a first word and a second word of the DMP, wherein each mark is recorded using a different laser power setting. In an embodiment all ranges of write power levels are used for recording the correction marks. The drive 2 is then placed in a mark quality verification mode and by "reading" back the correct mark, the microprocessor 48 determines which power level produces the best mark quality. The laser power setting for writing the correction mark is recorded in the third word of the DMP at the same time as the correction mark is recorded. In other words, the correction mark recorded at the selected power level can be verified so as to mark its quality immediately after the correction mark is written, and if the mark meets the mark quality criterion, the power level for recording the mark is recorded into the third word of the correction sector DMP area, and it is not necessary to write any further correction mark. If the mark does not meet the mark quality criterion, additional correction marks are recorded at different power levels and the mark quality is verified. Instead of using the entire calibration sector as a single power calibration test method, the sector may be divided into "micro-sectors". Thus, one micro-sector may be used for each calibration test, and the power level may be recorded in the DMP area of the micro-sector. It will be appreciated that alternative methods of determining the appropriate or optimum laser power level will generally use less space in the reserved area 170 than the previously described methods, and that it is possible to use one calibration sector for multiple calibration operations.

As described above, in order to avoid premature exhaustion of the calibration sector, it is preferable to reduce the number of times of calibrating the laser power as much as possible. Accordingly, a default power level may be programmed into the microprocessor 48. If a predetermined number of sectors cannot be verified during a recording operation (indicating that the laser power level may be incorrect), the microprocessor may initiate a calibration routine. In another embodiment (for multi-sector write operations), the first sector is recorded and its readability is tried to be verified. If the verification is successful (indicating that the power level is correct), the remaining sectors are recorded at the same power level. If the verification fails, the microprocessor 48 determines that a correction is needed. The first sector is then rewritten to the spare sector of the reserved area 170 and the remaining sectors are recorded to the user area 160 at the new corrected power level. Furthermore, after the remaining sectors are verified, the write power level can be readjusted, if necessary, to prepare for the next write instruction, thus further reducing the need to use additional calibration sectors.

The correction pattern may be composed of one 2T mark (mark), one 6T space (space), one 4T mark, and one 6T space repeated multiple times. A variety of modes can be used as long as the writing mode takes into account the thermal effect of the isolated write marks. A correction pattern written at too high a write laser power may generate too large a mark which in turn may affect the focusing and tracking process, so that the track following the laser beam 26 may be erroneous. Furthermore, the correction sector may not include error correction codes or resynchronization characters, so if written with wrong laser power levels, it is not possible to distinguish a reliable sector from a sector with many failures, which again supports isolation. Finally, the use of micro-sectors will create areas where no calibration sectors are recorded and represent a large number of media failures, which again supports isolation. Therefore, the correction sector and the spare sector in the reserved area 170 should not be mixed. An alternative is to use a table for determining whether a sector in the reserved area is to be used as a spare sector or a calibration sector in order to allow mixing of spare sectors and calibration sectors. Thereby avoiding the need to read or reliably seek over the data area of the calibration sector. A disadvantage of this scheme is that it consumes valuable disc space in order to save the table on a write-once medium. The table must be updated every time a sector is reserved or a correction segment is written, which again consumes additional space. Although it is possible to explicitly assign one set of addresses in the reserved area 170 to spare sectors and another set of independent addresses to calibration sectors, this predetermined, unchanging allocation of space is not necessarily suitable for all operating environments. For example, in an environment where data needs to be written to an optical disc relatively frequently, or where the optical disc needs to be mounted/removed frequently, or where only a small amount of data needs to be recorded in a write operation, the operating parameters may change frequently. At this point, recalibration may need to be performed frequently, such that all calibration sectors are exhausted before all data and spare sectors are exhausted. On the other hand, when the operating environment generally includes frequently recorded large blocks of data, the operating parameters are more stable, requiring less correction, but more spare sectors. Thus, the sector allocation between the spare sector and the calibration sector is preferably performed dynamically. In the present invention, as shown by arrows in fig. 4B, it is preferable that the spare sectors and the calibration sectors are expanded from both ends of the reserved area 170, rather than allocating a specific section in the reserved area 170 to the spare sectors and the remaining sections to the calibration sectors. In addition, due to seek problems associated with calibration sectors, it is preferable to use calibration sectors from the inner end (high address) 172 of the reserved area 170 toward the outer end (low address) while using spare sectors from the outer end 174 toward the inner end. Thus, regardless of the relative sector numbers used by the spare and calibration sectors, the available space in the reserved area 170 is only exhausted when there are no free sectors remaining in the reserved area 170.

The present invention also provides areas for spare sectors and calibration sectors on the optical disc 2 after the reserved area 170 of all extents is filled. Along the reserved area of extent 117, end extent 117 contains a general overflow reserved area 118 (FIG. 4A). The end extent 117 is the best location for the general overflow reserved area 118, as drive performance is typically worst in the end extent 117, and it is also undesirable to use high performance areas on the optical disc 10 for the general overflow reserved area. The general overflow reserve 118 is used in the same manner as the reserve 170, but the general overflow reserve 118 may contain spare and calibration sectors associated with more than one extent. Although the main reserved area 170 may not contain a pointer to the address of the general overflow reserved area 118, the drive 2 may be programmed to: when the drive 2 finds that the primary reserved area 170 is full, or the drive 2 cannot find spare sectors in the reserved area 170 to replace the previously recorded defective user sectors, the drive 2 looks for the general overflow reserved area 118. In other words, the driver 2 is programmed to: if the reserved area of a particular extent is full, the drive 2 finds the next available reserved area (i.e. the reserved area towards the next extent of ID 102) for correction purposes and finds the general overflow reserved area 118 for spare (since the optimum laser power level may vary from extent to extent, it is best to correct as close as possible to the ideal extent).

As described above, the media manufacturer may determine the size of each reserved area 170 if the medium is initialized by the manufacturer, otherwise, the size of the reserved area is determined by the user. In the latter case, the user generally determines the number of spare sectors and calibration sectors needed for the entire disc based on the particular operating environment and conditions. Then, the total number of both sectors is proportionally allocated among all the extents, according to the total number of sectors in each extent (for some disc formats, the total number of sectors in each extent differs from extent to extent). In other words, a default number may be provided and the user can double or double the value when initializing the optical disc 10. Subsequently, the microprocessor 48 calculates the start and end addresses of the respective user data areas 160 and the respective reserved areas 170 of each band, and the start and end addresses of the general overflow reserved area 118, and records the above information in a Disc Structure Table (DST) sector on the optical disc 10. The information in the DST enables the microprocessor to translate logical block addresses received from the host 44 into physical track and sector addresses on the optical disc 10.

Claims (19)

1. A method of correcting the laser write power in an optical drive (2), comprising the steps of:

installing a write-once optical disc (10) into a drive, said disc having a plurality of recording zones (112) and 117, each zone having a reserved area (170) comprising calibration sectors (130) and spare sectors (132), each zone further having a user area (160) comprising user data sectors;

moving the optical head to the selected disc zone (113);

determining whether the laser write power should be corrected;

if the laser write power should be corrected, finding unused first correction sectors (130) in a reserved area (170) of the selected disc zone;

writing a write power correction pattern into the first correction sector;

reading out a write power correction pattern from the first correction sector; and

a write power value for recording data on user data sectors (160) in a selected extent of the optical disc is determined.

2. A method as claimed in claim 1, further comprising the step of, if an unused first correction sector (130) is not found in the reserved area (170) of the selected disc zone (113):

finding unused second correction sectors in a general overflow area (118) of the optical disc (10);

writing a write power correction pattern into the second correction sector;

reading out a write power correction pattern from the second correction sector; and

a write power value is determined for recording data on user data sectors (160) of a selected extent (113) of the optical disc.

3. A method as claimed in claim 1, further comprising the steps of:

recording data at the determined write power value onto a selected user data sector (140) in the selected extent (113);

verifying the data recorded on the selected user sector;

if the verifying step fails, finding an unused first spare data sector (132) in a reserved area (170) of the selected extent (113);

recording the above data to a first spare data sector; and

the data recorded into the first spare data sector is verified.

4. A process as claimed in claim 3, wherein:

said step of finding unused first correction sectors (130) in a reserved area (170) of the selected disc zone (113) comprises: a step of finding an unused sector (172) closest to the first end of the reserved area; and

said step of finding unused first spare data sectors (132) in the reserved area of the selected extent comprises: a step of finding an unused sector (174) closest to the second end of the reserved area.

5. A method as claimed in claim 3, further comprising the step of, if no unused first spare data sectors are found in the reserved area (170) of the selected extent (113):

searching for unused second data spare sectors within a general overflow area (118) of the optical disc;

recording the above data to a second spare data sector; and

the data recorded on the second spare data sector is verified.

6. A process as claimed in claim 5, wherein:

said step of finding unused first correction sectors (130) in a reserved area (170) of the selected disc zone (113) comprises: a step of finding an unused sector (172) closest to the first end of the reserved area;

the step of finding unused first spare data sectors (132) in a reserved area of the selected extent comprises: a step of finding an unused sector (174) closest to the second end of the reserved area;

said step of finding unused second correction sectors in the general overflow area comprises: a step of finding an unused sector closest to a first end of the general overflow area (118); and

said step of finding unused second spare data sectors in the general overflow area comprises: a step of finding an unused sector closest to the second end of the general overflow area (118).

7. A method as claimed in claim 1, further comprising the steps of:

recording first data at a first write power value to a first user data sector (140) selected within the selected extent (113);

verifying the first data recorded on the selected first user sector;

if the verifying step fails, finding unused first calibration sectors (130) in a reserved area (170) of the selected extent;

performing the establishing, writing, reading and determining steps;

finding unused first spare data sectors (132) in a reserved area of the selected extent;

recording first data onto a first spare data sector;

verifying the first data recorded on the first spare data sector;

moving the optical head (10) radially to the selected disc zone; and

the remaining data is recorded to the second sector of the selected extent at the determined write power value.

8. An optical disc (10) comprising:

a spiral track extending between inner and outer diameter locations, the spiral track having a plurality of logical tracks, each logical track divided into a plurality of data extents (112-117);

a plurality of predetermined primary data sectors (140) within each of said data extents (113); and

a reserved area (170) having a plurality of predetermined sectors;

the method is characterized in that:

the optical disc is a write-once optical disc; and

each of the data disk regions (112-117) has a reserved area (170), each of which may be used as a spare sector (132) or a calibration sector (130).

9. A write-once optical disc (10) as claimed in claim 8, further comprising a general overflow area (118) having a plurality of predetermined sectors, each sector being usable as a spare sector or a calibration sector.

10. The optical write-once disc (10) of claim 9, wherein:

the universal spill zone (118) having a first end and a second end; and

during a recording operation, sectors for spare in the general overflow area are used in a direction starting from a nearest unused sector; and the general overflow area for correction is in the opposite direction, i.e. starting from the unused sector closest to the second end to the first end.

11. The optical write-once disc (10) of claim 8, wherein:

each of the reserved areas (170) having a first end (172) and a second end (174); and

during a recording operation, sectors in the reserved area for spare are used in a direction starting from an unused sector closest to the first end to the second end; whereas the sectors used for correction in the reserved area are used in the opposite direction, i.e. starting from the unused sector closest to the second end to the first end.

12. A write-once optical disc (10) as claimed in claim 8, wherein the sectors within the disc zone (113) comprise a header zone (144) and a user data zone (160).

13. A write-once optical disc (10) according to claim 12, wherein said data area of the main data sector comprises:

a first section in which an address of the main data sector can be recorded;

a second zone in which an address of the reserved area of the extent can be recorded; and

and a third section in which the laser correction value is recorded.

14. The write-once optical disc (10) of claim 12, wherein said data area of the spare sector (132) includes:

a first section in which an address of the spare sector can be recorded;

a second zone in which an address of a main defect data area of the extent can be recorded; and

and a third section in which the laser correction value is recorded.

15. The write-once optical disc (10) of claim 12, wherein said data area of the calibration sector (130) comprises:

a first section in which at least a partial correction pattern can be recorded; and

a second section in which the laser correction values are recorded.

16. A system (2) for recording data on an optical disc (10), the system having a loading mechanism, a spindle motor (16) capable of mounting the optical disc, an interface (42) for transmitting data to and receiving commands from a host (44), a laser light source (28), an optical head (for recording data to and reading data from the optical disc), a regulator (24) for moving the optical head, and a controller (for managing the loading mechanism, the spindle motor, the interface, the optical head, and the regulator), the system further comprising:

a processor (48) for determining when to initiate laser write power correction;

means (32, 22) for directing a laser beam from said laser to a first calibration sector (130) in said reserved area (170) at the start of calibration;

means for writing a correction pattern to the correction sector;

means for reading the correction pattern and determining an adjusted write power level;

means for setting a write power level to an adjusted write power level;

means for recording first data into a predetermined data sector (140) in the user area (160);

means for verifying the first data;

means for directing a beam (26) from said laser (28) to a second predetermined sector (132) within said reserved area upon a failure to verify; and

means for re-recording the first data to the second predetermined sector.

The method is characterized in that:

the optical disc is a write-once optical disc; and

the optical disc has a plurality of recording zones (112-117), each zone having a reserved area (170) comprising calibration sectors (130) and spare sectors (132), and a user area (160) comprising user data sectors.

17. A data recording system as claimed in claim 16, wherein:

the means for directing a light beam (26) into a first correction sector (130) within the retention area (170) comprises: means for directing the beam onto a first predetermined sector within a first end of said reserved area (170); and

said means for directing the beam to a second predetermined sector (132) within said reserved area comprising: means for directing the beam to a second predetermined sector within a second end of the reserved area opposite the first end.

18. A data recording system as claimed in claim 16, wherein said means for recording the first data (146) in the predetermined data sector (140) comprises: means for recording the address of the predetermined data sector in a first word of the predetermined data sector, means for recording the start address of said reserved area in a second word of the predetermined data sector, and means for recording the laser write power level in a third word of the predetermined data sector.

19. A data recording system as claimed in claim 16, further comprising:

means for receiving input from a user indicating a sector of said reserved area (170) to be allocated to each disc area (112-117); and

means for determining the start and end addresses of the reserved areas of each extent.