Pseudo-overwriting data on write-once discs
View Patent ↗A file system which is enabled to use a Metadata Partition instead of VAT for write-once discs, is provided by a pseudo-overwrite method. On applying this invention to a drive apparatus which supports pseudo-overwrite media, the file system distinguishes data to overwrite from data to append. When the data is newly written to a logical sector, the drive apparatus writes the data to a physical sector to which the logical sector corresponds. When the logical sector is overwritten the data is written to another unrecorded physical sector in the volume space, and remapping information that specifies the original address, and the remapping address are stored in the remapping table.
1. A recording method for instructing a drive apparatus having a pseudo-overwrite function to write data on a write-once disc,
the recording method comprising the steps of:
(a) receiving a write request which specifies at least data for a file to be written;
(b) instructing the drive apparatus to read metadata for managing the file from a location in the write-once disc, so as to obtain the metadata;
(c) querying a first next writable address indicating a location at which data is to be written next to the drive apparatus, so as to obtain the first next writable address;
(d) updating the metadata to reflect the writing of the data specified by the write request;
(e) instructing the drive apparatus to write the data specified by the write request to a location indicated by the first next writable address in the write-once disc;
(f) instructing the drive apparatus to write at least a part of the updated metadata to the location from which the metadata is read in the step (b) in the write-once disc, wherein the drive apparatus obtains a second next writable address and when the location from which the metadata is read is smaller than the second next writable address, records the updated metadata at a location indicated by the second next writable address, and
(g) updating a remapping table to include an entry which specifies a physical address corresponding to the location from which the metadata is read and a new physical address where the updated metadata is written.
2. A recording method according to claim 1 , wherein the steps (e) and (f) are performed using the same write instruction.
3. A recording method according to claim 1 , wherein the step (f) is performed after the step (e) is performed.
4. A recording method according to claim 1 , wherein the updated metadata includes a file entry of a directory under which the file is recorded.
5. A recording method according to claim 1 , wherein the updated metadata includes a file entry of the file.
6. A system controller for instructing a drive apparatus having a pseudo-overwrite function to write data on a write-once disc,
the system controller comprising a controller for controlling the drive apparatus, wherein the controller is configured to perform a process including the steps of:
(a) receiving a write request which specifies at least data for a file to be written;
(b) instructing the drive apparatus to read metadata for managing the file from a location in the write-once disc, so as to obtain the metadata;
(c) querying a first next writable address indicating a location at which data is to be written next to the drive apparatus, so as to obtain the first next writable address;
(d) updating the metadata to reflect the writing of the data specified by the write request;
(e) instructing the drive apparatus to write the data specified by the write request to a location indicated by the first next writable address in the write-once disc;
(f) instructing the drive apparatus to write at least a part of the updated metadata to the location from which the metadata is read in the step (b) in the write-once disc, wherein the drive apparatus obtains a second next writable address and when the location from which the metadata is read is smaller than the second next writable address, records the updated metadata at a location indicated by the second next writable address, and
(g) updating a remapping table to include an entry which specifies a physical address corresponding to the location from which the metadata is read and a new physical address where the updated metadata is written.
7. A system controller according to claim 6 , wherein the controller includes a semiconductor integrated circuit.
8. A non-transitory machine readable medium having a program stored thereon for use in a system controller for instructing a drive apparatus having a pseudo-overwrite function to write data on a write-once disc,
wherein the program is configured to perform a process including the steps of:
(a) receiving a write request which specifies at least data for a file to be written;
(b) instructing the drive apparatus to read metadata for managing the file from a location in the write-once disc, so as to obtain the metadata;
(c) querying a first next writable address indicating a location at which data is to be written next to the drive apparatus, so as to obtain the first next writable address;
(d) updating the metadata to reflect the writing of the data specified by the write request;
(e) instructing the drive apparatus to write the data specified by the write request to a location indicated by the first next writable address in the write-once disc;
(f) instructing the drive apparatus to write at least a part of the updated metadata to the location from which the metadata is read in the step (b) in the write-once disc, wherein the drive apparatus obtains a second next writable address and when the location from which the metadata is read is smaller than the second next writable address, records the updated metadata at a location indicated by the second next writable address, and
(g) updating a remapping table to include an entry which specifies a physical address corresponding to the location from which the metadata is read and a new physical address where the updated metadata is written.