1. A data storage system, comprising:
a solid-state non-volatile memory array comprising blocks including a block and a neighboring block, the block associated with a plurality of zones including a first zone and a second zone, each zone of the plurality of zones including one or more pages of the block; and
a controller configured to:
write data to, and read the data from, the memory array in response to memory access commands received from a host system; and
scan the memory array for memory errors with (1) a scan frequency of the one or more pages of the first zone depending at least on a position of a page of the first zone within the block relative to a physical block boundary separating the block from the neighboring block and (2) a scan frequency of the one or more pages of the second zone depending at least on a position of a page of the second zone within the block relative to the physical block boundary,
wherein the position of the page in the first zone is located closer to the physical block boundary than the position of the page in the second zone, and the controller is configured to scan the one or more pages of the first zone for the memory errors more frequently than the one or more pages of the second zone.
2. The data storage system of claim 1, wherein the memory errors comprise endurance-related memory errors, and the first zone comprises a first group of contiguous pages of the block and the second zone comprises a second group of contiguous pages of the block not overlapping with the first group of contiguous pages.
3. The data storage system of claim 1, wherein the block has a block size equal to a size of a smallest grouping of pages of the memory array which is erasable in a single operation by the controller.
4. The data storage system of claim 1, wherein the neighboring block is a subsequent neighboring block to the block.
5. In a data storage subsystem comprising a controller and a non-volatile memory array comprising a plurality of blocks, each block of the plurality of blocks comprising a plurality of pages, a method of scanning for memory errors of the non-volatile memory array, the method comprising:
determining priorities for scanning a plurality of zones of a block of the plurality of blocks for the memory errors based at least in part on a quality attribute of each zone of the plurality of zones, each zone of the plurality of zones comprising one or more pages of the block; and
scanning the one or more pages of the plurality of zones for the memory errors based on the determined priorities so that the one or more pages of a first zone of the plurality of zones comprising a first quality attribute are scanned more frequently than the one or more pages of a second zone of the plurality of zones comprising a second quality attribute,
wherein the first quality attribute depends at least on a physical position of a page of the first zone within the block, and the second quality attribute depends at least on a physical position of a page of the second zone within the block.
6. The method of claim 5, wherein said scanning the one or more pages of the plurality of zones comprises:
checking the one or more pages of the first zone for the memory errors;
determining whether a count of the memory errors for the first zone exceeds a threshold; and
when the count of the memory errors for the first zone exceeds the threshold, recovering at least some data stored in the one or more pages of the first zone and adjusting the first quality attribute to reflect a lower level of reliability or endurance.
7. The method of claim 5, wherein the first quality attribute further depends at least on one of: an operational characteristic of the one or more pages of the first zone, a measured performance of the one or more pages of the first zone, and an environmental characteristic of the non-volatile memory array.
8. The method of claim 5, wherein the first quality attribute further depends at least on a number of program-erase cycles performed on the one or more pages in the first zone.
9. The method of claim 5, wherein said determining the priorities for scanning comprises determining the priorities using a weighted round robin scheduling based at least in part on the quality attribute of each zone.
10. The method of claim 5, further comprising:
periodically measuring environmental conditions of the non-volatile memory array;
determining an environmental condition metric based on the measured environmental conditions; and
based on a comparison of the environmental condition metric to a threshold metric:
randomly selecting a set of zones from the plurality of zones irrespective of the determined priorities; and
scanning the one or more pages of the set of zones for the memory errors.
11. The method of claim 5, wherein the first zone comprises a first group of contiguous pages of the block, and the second zone comprises a second group of contiguous pages of the block not overlapping with the first group of contiguous pages.
12. The method of claim 5, wherein the first quality attribute depends at least on the physical position of the page of the first zone within the block with respect to a physical block boundary separating the block from a subsequent neighboring block, and the second quality attribute depends at least on the physical position of the page of the second zone within the block with respect to the physical block boundary.
13. A data storage subsystem comprising a controller configured to communicate with a non-volatile memory array comprising a plurality of blocks, each block of the plurality of blocks comprising a plurality of pages,
wherein the controller is configured to:
determine priorities for scanning a plurality of zones of a block of the plurality of blocks for memory errors based at least in part on a quality attribute of each zone, each zone of the plurality of zones comprising one or more pages of the block; and
scan the one or more pages of the plurality of zones for the memory errors based on the determined priorities so that the one or more pages of a first zone of the plurality of zones comprising a first quality attribute are scanned more frequently than the one or more pages of a second zone of the plurality of zones comprising a second quality attribute, and
wherein the first quality attribute depends at least on a physical position of a page of the first zone within the block, and the second quality attribute depends at least on a physical position of a page of the second zone within the block.
14. The data storage subsystem of claim 13, wherein when the controller scans the first zone, the controller is configured to:
check the one or more pages of the first zone for the memory errors;
determine whether a count of the memory errors for the first zone exceeds a threshold; and
when the count of the memory errors for the first zone exceeds the threshold, recover at least some data stored in the first zone and adjust the first quality attribute to reflect a lower level of reliability or endurance.
15. The data storage subsystem of claim 13, wherein the first quality attribute further depends at least on one of: an operational characteristic of the one or more pages of the first zone, a measured performance of the one or more pages of the first zone, and an environmental characteristic of the non-volatile memory array.
16. The data storage subsystem of claim 13, wherein the first quality attribute further depends at least on a number of program-erase cycles performed on one or more pages in the first zone.
17. The data storage subsystem of claim 13, wherein the controller is further configured to determine priorities for scanning using a weighted round robin scheduling based at least in part on the quality attribute of each zone.
18. The data storage subsystem of claim 13, wherein the controller is further configured to:
periodically measure environmental conditions of the non-volatile memory array;
determine an environmental condition metric based on the measured environmental conditions; and
based on a comparison of the environmental condition metric to a threshold metric:
randomly select a set of zones from the plurality of zones; and
scan the one or more pages of the set of zones for the memory errors.
19. The data storage subsystem of claim 13, wherein the first zone comprises a first group of contiguous pages of the block, and the second zone comprises a second group of contiguous pages of the block not overlapping with the first group of contiguous pages.
20. The data storage subsystem of claim 13, wherein the first quality attribute depends at least on the physical position of the page of the first zone within the block with respect to a physical block boundary separating the block from a subsequent neighboring block, and the second quality attribute depends at least on the physical position of the page of the second zone within the block with respect to the physical block boundary.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. An image forming apparatus having a first image forming unit and a second image forming unit, the first and second image forming units forming images by different methods on a single page, wherein the second image forming unit forms an identifying image and the first image forming unit forms an image different from the identifying image.
2. The image forming apparatus of claim 1, wherein the identifying image identifies an original image to distinguish the original image from copies thereof.
3. The image forming apparatus of claim 1, wherein the identifying image is formed by both the first and second image forming units.
4. The image forming apparatus of claim 1, wherein one of the first image forming unit and the second image forming unit has an impact mechanism for forming images on multiple-ply pressure-sensitive media.
5. The image forming apparatus of claim 1, wherein at least one of the first image forming unit and the second image forming unit forms an image differing in color from background parts of the page.
6. The image forming apparatus of claim 5, wherein the first image forming unit and the second image forming unit both form images differing in color from background parts of the page, the first image forming unit using a first coloring agent, the second image forming unit using a second coloring agent different from the first coloring agent.
7. The image forming apparatus of claim 6, wherein the first coloring agent is a toner agent and the second coloring agent is an ink agent.
8. The image forming apparatus of claim 1, wherein at least one of the first image forming unit and the second image forming unit has a mechanism that deforms the page.
9. The image forming apparatus of claim 8, wherein said mechanism is an impact mechanism for striking the page.
10. The image forming apparatus of claim 9, wherein the first image forming unit and the second image forming unit form images on mutually reverse sides of the page.
11. The image forming apparatus of claim 9 wherein the page has a first side and a second side, the first image forming unit forms an image on the first side of the page, the image formed by the first image forming unit differing in color from background parts of the first side of the page, and the second image forming unit forms an image on the first side of the page by striking the second side of the page.
12 The image forming apparatus of claim 8, wherein said mechanism is a punching mechanism for punching holes in the page.
13 The image forming apparatus of claim 1, wherein the first image forming unit is an ink jet printing unit.
14 The image forming apparatus of claim 1, wherein the first image forming unit is an electrophotographic printing unit.
15 The image forming apparatus of claim 1, wherein the second image forming unit is a serial impact dot matrix printing unit.
16. The image forming apparatus of claim 1, wherein the second image forming unit forms a fixed image.
17. The image forming apparatus of claim 16, further comprising a receiving unit for receiving first data and a storage unit for storing second data, wherein the first image forming unit forms an image according to the first data and the second image forming unit forms the fixed image according to the second data.
18. The image forming apparatus of claim 1, further comprising rollers for transporting the page through the first image forming unit and then through the second image forming unit.
19. The image forming apparatus of claim 18, wherein the rollers create slack in the page between the first image forming unit and the second image forming unit.