Cooperative storage device with host-accessible subdivisions
This disclosure provides techniques hierarchical address virtualization within a memory controller and configurable block device allocation. By performing address translation only at select hierarchical levels, a memory controller can be designed to have predictable I/O latency, with brief or otherwise negligible logical-to-physical address translation time. In one embodiment, address transition may be implemented entirely with logical gates and look-up tables of a memory controller integrated circuit, without requiring processor cycles. The disclosed virtualization scheme also provides for flexibility in customizing the configuration of virtual storage devices, to present nearly any desired configuration to a host or client.
1 . A storage device comprising:
at least one namespace;
flash memory having subdivisions, the subdivisions comprising respective, non-overlapping sets of erase units; and
logic operable to cause the storage device to transmit to a host, responsive to receipt of at least one query from the host, information identifying a specific namespace of the at least one namespace, one or more of the subdivisions and, for each one of the one or more subdivisions, an associated subdivision size; and
logic operable to cause the storage device to receive write requests and, for a first one of the write requests, to:
derive, from address information associated with the first one of the write requests, a first address portion, a second address portion, and a third address portion, and
identify, from the first address portion, the specific namespace, and
identify, from the second address portion, an addressed subdivision of the one or more identified subdivisions, and
identify from the third address portion, a logical block address, and
program data associated with the first write request into a physical storage location within a specific erase unit in the set which is respective to the addressed subdivision; and
logic operable to cause the storage device to track validity status for the physical storage location; and
logic operable to cause the storage device to receive a deallocate command that specifies the logical block address and to, responsive to receipt of the deallocate command, update the validity status to indicate that the physical storage location is released; and
logic operable to cause the storage device to automatically detect a condition where (1) the specific erase unit has at least a threshold amount of storage that has been released, and (2) all storage locations of the specific erase unit, including the physical storage location, are each at least one of ( 2 a ) released, or ( 2 b ) contain no valid data, and to responsively and automatically control physical erasure of the specific erase unit; and
logic operable to cause the storage device to store metadata associated with the specific erase unit, the metadata indicating one of an erase count or wear information, and to update the metadata in association with the physical erasure of the specific erase unit; and
logic operable to cause the storage device to, in connection with the physical erasure of the specific erase unit, detect that the specific erase unit is bad, and to responsively update data tracked by the storage device to mark the specific erase unit as bad;
wherein each said logic comprises at least one of circuitry or instructions stored on a physical storage medium that, when executed, are to control circuitry of the storage device.
2 . The storage device of claim 1 , wherein the storage device further comprises logic operable to cause the storage device to:
track second metadata, the second metadata corresponding to the addressed subdivision;
compare the second metadata with a criterion; and
responsive to satisfaction of the criterion by the second metadata, automatically copy valid data from at least one erase unit, of the set which is respective to the addressed subdivision, to a new erase unit.
3 . The storage device of claim 2 , wherein the storage device further comprises logic operable to cause the storage device to:
in association with the copy of valid data from the at least one erase unit to the new erase unit, disassociate the at least one erase unit from the set which is respective to the addressed subdivision; and
automatically control physical erasure of the at least one erase unit.
4 . The storage device of claim 2 , wherein the storage device further comprises logic operable to cause the storage device to:
maintain a pool of free erase units; and
select the new erase unit from the pool of free erase units, and assign the new erase unit to the set which is respective to the addressed subdivision.
5 . The storage device of claim 2 , wherein the second metadata comprises aggregate data validity information associated with multiple physical storage locations of the at least one erase unit.
6 . The storage device of claim 2 , wherein the second metadata represents a time since data was programmed in the at least one erase unit.
7 . The storage device of claim 2 , wherein the second metadata indicates wear of the at least one erase unit.
8 . The storage device of claim 2 , wherein the second metadata indicates a data access frequency associated with logical block addresses mapped to the at least one erase unit.
9 . The storage device of claim 1 , wherein the at least one query comprises one or more first queries, and wherein the storage device further comprises a host interface and logic operable to cause the storage device to:
track second metadata respective to different ones of the subdivisions;
receive, via the host interface, a second query from the host; and
responsive to the second query, transmit information, to the host, which is dependent on the tracked second metadata.
10 . The storage device of claim 9 , wherein the second query specifies a given subdivision of the different ones of the subdivisions and wherein the information transmitted to the host indicates a quantity of available space, associated with the set of erase units respective to the given one of the different ones of the subdivisions, which can currently be written to.
11 . The storage device of claim 9 , wherein the second metadata represents a time since data was programmed into the respective subdivision.
12 . The storage device of claim 1 , wherein the at least one query comprises one or more first queries, and wherein the storage device further comprises logic operable to cause the storage device to:
store a value representing a maximum number of the subdivisions; and
receive a second query; and
responsively transmit, to the host, information representing the maximum number of the subdivisions.
13 . The storage device of claim 1 , wherein:
the at least one query comprises one or more first queries;
the flash memory comprises flash memory dies;
the flash memory further comprises one or more die groups, each die group having a subset of one or more of the flash memory dies, the one or more of the flash memory dies in each die group being mutually-exclusive to the one or more of the flash memory dies in each other die group, wherein each die group is associated with an identifier (ID); and
the storage device further comprises logic operable to cause the storage device to receive a second query from the host, and to responsively transmit, to the host, information representing each ID associated with the one or more die groups.
14 . The storage device of claim 13 , wherein, for the first one of the write requests, the logic is further operable to cause the storage device to perform a division operation, on the address information, to identify the ID which is associated with a specific die group of the one or more die groups.
15 . The storage device of claim 1 , wherein the storage device further comprises logic operable to cause the storage device to:
receive a configuration command, from the host, and responsively establish a value of a setting; and
responsively update a quantity, of the one or more subdivisions, dependent on the value of the setting.
16 . The storage device of claim 1 , wherein:
the storage device further comprises logic operable to cause the storage device to receive a read request from the host, the read request being directed to the identified logical block address; and
the logic is further operable to cause the storage device to:
detect an error condition associated with reading of the programmed data;
responsively copy valid data from the specific erase unit to a new erase unit; and
update a logical-to-physical look-up table, such that the identified logical block address is indexed to a physical storage location within the new erase unit.
17 . The storage device of claim 16 , wherein the error condition corresponds to a bit error rate which exceeds a threshold.
18 . The storage device of claim 1 , wherein the storage device further comprises logic operable to cause the storage device to maintain a logical-to-physical look-up table and to, in response to receiving the first one of the write requests, update the logical to physical look-up table, such that the identified logical block address is indexed to the physical storage location.
19 . The storage device of claim 1 , wherein the storage device further comprises logic operable to cause the storage device to maintain information identifying a next-available physical storage location for the addressed subdivision, and to automatically update, in association with the receipt of the first one of the write requests, the information identifying the next-available physical storage location.
20 . The storage device of claim 1 , wherein the logic is further operable to cause the storage device to, for the first one of the write requests, identify a value and perform a division operation on the value, wherein a quotient of the division operation comprises at least one of a number of the erase units, or a number of pages, or a number of storage locations, and wherein a remainder of the division operation corresponds to a structural offset corresponding to a physical address in the flash memory.
21 . The storage device of claim 1 , wherein the associated subdivision size corresponds to at least a minimum amount of storage capacity to be physically reset by the storage device as part of a physical memory erasure operation.
22 . The storage device of claim 1 , wherein the storage device further comprises logic operable to cause the storage device to perform garbage collection and, in connection with said garbage collection, to:
relocate all remaining valid data from any erase unit in the set respective to the addressed subdivision to one or more new erase units; and
automatically associate the set respective to the addressed subdivision with the one or more new erase units, such that the one or more new erase units are not used to store data associated with any other of the subdivisions of the flash memory.
23 . The storage device of claim 18 , wherein:
the storage device further comprises logic operable to cause the storage device to receive a read request, from the host, the read request being directed to the identified logical block address; and
the logic is further operable to cause the storage device to:
retrieve, from the logical-to-physical look-up table, a physical address of the physical storage location; and
retrieve, from the flash memory, and according to the retrieved physical address, the programmed data, and responsively transmit the retrieved, programmed data to the host.
24 . The storage device of claim 18 , wherein the write requests are first write requests and wherein the storage device further comprises logic operable to cause the storage device to receive, from the host, a second write request, the second write request being directed to the addressed subdivision and, in association with the second write request, to:
detect that insufficient free memory space remains in the set of erase units respective to the addressed subdivision;
assign a new erase unit to the set respective to the addressed subdivision;
identify a destination physical address associated with a storage location in the new erase unit;
store write data accompanying the second write request at the identified storage location in the new erase unit; and
update the logical to physical look-up table to index a logical block address, identified for the second write request, to the destination physical address.
25 . The storage device of claim 24 , wherein:
the logical block address identified for the second write request corresponds to the logical block address identified for the first one of the write requests; and
the logic is further operable to cause the storage device to update, in association with the storage of the write data accompanying the second write request, the logical-to-physical look-up table, so as to reindex the identified logical block address to the destination physical address.
26 . The storage device of claim 1 , wherein the storage device further comprises logic operable to cause the storage device to, responsive to the automatic detection of the condition, automatically copy remaining valid data from the specific erase unit to a new erase unit, and wherein the physical erasure of the specific erase units is performed after the automatic copy of the remaining valid data.
27 . The storage device of claim 26 , wherein the storage device further comprises logic operable to cause the storage device to:
maintain a pool of free erase units; and
select the new erase unit from the pool of free erase units, and assign the new erase unit to the set which is respective to the addressed subdivision.