System data storage mechanism providing coherency and segmented data loading
A data storage subsystem is disclosed that implements a process for storing and/or reconstructing system data, such as a system mapping table. In certain embodiments, table pages are systematically copied, or flushed, to non-volatile memory in a progressive manner, according to a fixed ratio of flushed table pages per table update trigger, thereby facilitating write and/or load efficiency. Full or partial reconstruction of a table may be performed within a bounded number of operations based on the size of the table, the ratio implemented, and/or other characteristics.
1. A data storage system, comprising:
a volatile memory;
a non-volatile memory; and
a controller configured to cause:
updating at least a page of a system table in the volatile memory, wherein when the at least a page is updated, the controller is configured to cause:
flushing, from the volatile memory to the non-volatile memory, the updated at least a page in the volatile memory; and
flushing, from the volatile memory to the non-volatile memory, one or more additional pages of the system table in the volatile memory, based at least on a predetermined ratio of a predetermined count of flushed pages per system table update trigger event, wherein the one or more additional pages are different than the at least a page; and
reconstructing one or more pages of the system table stored in the non-volatile memory to the volatile memory.
2. The data storage system of claim 1 , wherein a sum of a count of the flushed at least a page and a count of the flushed one or more additional pages is equal to or less than the predetermined count of flushed pages.
3. The data storage system of claim 1 , wherein:
when the at least a page is updated in the volatile memory, the one or more additional pages are not updated in the volatile memory in response to the updating of the at least a page, and
a count of the one or more additional pages does not exceed a total count of pages of the system table in the volatile memory.
4. The data storage system of claim 2 , wherein the controller configured to cause updating at least a page of the system table in the volatile memory comprises:
the controller configured to cause, flushing the updated at least a page and the one or more additional pages, in response to one system table update trigger initiated by a host command.
5. The data storage system of claim 1 , wherein the controller configured to cause reconstructing one or more pages of the system table comprises:
the controller configured to cause reconstructing the system table to the volatile memory, using not more than a threshold count of read operations,
wherein the threshold count of read operations is less than or equal to T*((R+1)/R),
wherein T is a total count of pages in the system table, and
wherein R is an integer value.
6. The data storage system of claim 5 , wherein R is the predetermined ratio of the predetermined count of flushed pages per system table update trigger event.
7. The data storage system of claim 1 , wherein the controller configured to cause reconstructing one or more pages of the system table comprises the controller configured to cause:
loading one or more segments from the non-volatile memory to the volatile memory, wherein one or more pages of the system table in the non-volatile memory are divided into the one or more segments; and
recovering the system table using a number of operations less than or equal to twice a size of the system table measured in segments.
8. The data storage system of claim 7 , wherein content of the one or more segments has not been previously loaded to the volatile memory.
9. The data storage system of claim 8 , wherein the controller configured to cause reconstructing one or more pages of the system table comprises the controller configured to cause:
determining whether a data access request, accessing an address within a yet-to-be loaded segment of the system table, is pending; and
processing a segment associated with the address of the data access request, when the data access request accessing the address within the yet-to-be loaded segment of the system table is determined to be pending,
wherein the processing comprises:
determining that content of the segment has not been previously loaded to the volatile memory; and
loading the segment to the volatile memory.
10. The data storage system of claim 7 , wherein when no data access request is pending, a first of the one or more segments loaded to the volatile memory comprises a segment associated with one or more pages that have been most recently stored to the non-volatile memory.
11. The data storage system of claim 7 , wherein when no data access request is pending, a first of the one or more segments loaded to the volatile memory comprises a segment associated with an oldest valid page stored in the non-volatile memory.
12. A machine-implemented method, comprising:
updating at least a page of a system table in a volatile memory;
when the at least a page is updated:
flushing, from the volatile memory to a non-volatile memory, the updated at least a page in the volatile memory; and
flushing, from the volatile memory to the non-volatile memory, one or more additional pages of the system table in the volatile memory, based at least on a predetermined ratio of a predetermined count of flushed pages per system table update trigger event; and
reconstructing one or more pages of the system table stored in the non-volatile memory to the volatile memory.
13. The machine-implemented method of claim 12 , wherein:
when the at least a page is updated in the volatile memory, the one or more additional pages are not updated in the volatile memory in response to the updating of the at least a page, and
a count of the one or more additional pages does not exceed a total count of pages of the system table in the volatile memory.
14. The machine-implemented method of claim 12 , wherein the reconstructing one or more pages of the system table comprises:
reconstructing the system table to the volatile memory, using not more than a threshold count of read operations,
wherein the threshold count of read operations is less than or equal to T*((R+1)/R),
wherein T is a total count of pages in the system table, and
wherein R is an integer value.
15. The machine-implemented method of claim 14 , wherein R is the predetermined ratio of the predetermined count of flushed pages per system table update trigger event.
16. The machine-implemented method of claim 12 , wherein the reconstructing one or more pages of the system table comprises:
loading one or more segments from the non-volatile memory to the volatile memory,
wherein one or more pages of the system table in the non-volatile memory are divided into the one or more segments, and
wherein content of the one or more segments has not been previously loaded to the volatile memory;
when a data access request, accessing an address within a yet-to-be loaded segment of the system table, is pending:
loading a segment associated with the address of the data access request, to the volatile memory, when content of the segment has not been previously loaded to the volatile memory; and
recovering the system table using a number of operations less than or equal to twice a size of the system table measured in segments.
17. An apparatus, comprising:
means for updating at least a page of a system table in a volatile memory, wherein the means for updating comprises:
means for flushing, from the volatile memory to a non-volatile memory, the updated at least a page in the volatile memory; and
means for flushing, from the volatile memory to the non-volatile memory, one or more additional pages of the system table in the volatile memory, based at least on a predetermined ratio of a predetermined count of flushed pages per system table update trigger event, wherein the one or more additional pages are different than the at least a page; and
means for reconstructing one or more pages of the system table stored in the non-volatile memory to the volatile memory.
18. The apparatus of claim 17 , wherein:
when the at least a page is updated in the volatile memory, the one or more additional pages are not updated in the volatile memory in response to the updating of the at least a page, and
a count of the one or more additional pages does not exceed a total count of pages of the system table in the volatile memory.
19. The apparatus of claim 17 , wherein the means for reconstructing one or more pages of the system table comprises:
means for reconstructing the system table to the volatile memory, using not more than a threshold count of read operations,
wherein the threshold count of read operations is less than or equal to T*((R+1)/R),
wherein T is a total count of pages in the system table, and
wherein R is the predetermined ratio of the predetermined count of flushed pages per system table update trigger event.
20. The apparatus of claim 17 , wherein the means for reconstructing one or more pages of the system table comprises:
means for loading one or more segments from the non-volatile memory to the volatile memory,
wherein one or more pages of the system table in the non-volatile memory are divided into the one or more segments, and
wherein content of the one or more segments has not been previously loaded to the volatile memory;
when a data access request, accessing an address within a yet-to-be loaded segment of the system table, is pending:
means for loading a segment associated with the address of the data access request, to the volatile memory, when content of the segment has not been previously loaded to the volatile memory; and
means for recovering the system table using a number of operations less than or equal to twice a size of the system table measured in segments.