Data storage device and method for using zones of memory in a read scrub operation
A read to a wordline can cause a read disturb error on neighboring wordlines. Instead of scanning the entire memory to identify wordlines that have a read disturb problem, a localized read scan approach can be used. In this approach, the memory is organized into several zones, where each zone contains several wordlines. The number of reads in each zone is tracked, and, after a certain number of reads, the data in the zone is read. If the error rate of the data exceeds a threshold, the data is relocated to another area of the memory.
1. A data storage device comprising:
a memory comprising a block configured to be organized into a plurality of zones of wordlines, each zone comprising a plurality of wordlines; and
a processor coupled with the memory and configured to:
track a number of times each of the plurality of zones has been read; and
in response to a zone of the plurality of zones being read more than a threshold number of times:
read data from at least some of the wordlines in the zone;
determine if an error rate of the read data exceeds an error threshold; and
in response to determining that the error rate exceeds the error threshold, write data of the zone in another area of the memory instead of performing a read scrub operation on an entirety of the block based on a number of times the block has been read.
2. The data storage device of claim 1 , wherein the processor is further configured to track the number of times each of the plurality of zones has been read by maintaining a counter for each of the plurality of zones.
3. The data storage device of claim 1 , wherein the processor is further configured to track the number of times each of the plurality of zones has been read using a hash table.
4. The data storage device of claim 3 , wherein length or size of the hash table is a prime number.
5. The data storage device of claim 1 , wherein the processor is further configured to generate a unique identifier for each of the plurality of zones.
6. The data storage device of claim 5 , wherein the unique identifier is generated from one or more of the following: a metablock number, a plane-block number, a physical block number, and a wordline zone number.
7. The data storage device of claim 1 , wherein the threshold number of times is configurable.
8. The data storage device of claim 1 , wherein a number of wordlines in each of the plurality of zones is configurable.
9. The data storage device of claim 1 , wherein the memory comprises a three-dimensional memory.
10. In a data storage device comprising a memory comprising a block organized into a plurality of zones of wordlines, each zone comprising a plurality of wordlines, a method comprising:
receiving a read command from a host;
generating a unique identifier based on a physical location in the memory that is associated with the read command, wherein the unique identifier is associated with one of the plurality of zones and wherein the physical location comprises a physical address;
searching for the unique identifier in a hash table that tracks how many times each of the plurality of zones has been read;
in response to finding the unique identifier in the hash table, increasing a counter value in an entry in the hash table that is associated with the unique identifier;
determining whether the counter value exceeds a first threshold;
in response to determining that the counter value exceeds the first threshold, determining whether a bit error rate of data in the zone associated with the unique identifier exceeds a second threshold; and
in response to determining that the bit error rate exceeds the second threshold, move the data to another location in the memory instead of performing a read scrub operation on an entirety of the block based on a number of times the block has been read.
11. The method of claim 10 , wherein a number of entries in the hash table is a prime number.
12. The method of claim 10 , wherein the unique identifier is generated from one or more of the following: a metablock number, a plane-block number, a physical block number, and a wordline number.
13. The method of claim 10 , further comprising:
in response to not finding the unique identifier in the hash table, determining whether a tracking list in the hash table is full.
14. The method of claim 13 , further comprising:
in response to determining that the tracking list in the hash table is full, identifying a first unique identifier with a lowest counter value and replacing the first unique identifier with the unique identifier.
15. The method of claim 13 , further comprising:
in response to determining that the tracking list in the hash table is not full, adding the unique identifier to the tracking list.
16. The method of claim 13 , further comprising:
adding an index of the unique identifier to a next available index in response to the index of the unique identifier colliding with available indices.
17. A data storage device comprising:
a memory comprising a blosk configured to be organized into a plurality of zones of wordlines, each zone comprising a plurality of wordlines;
means for generating a unique identifier based on a physical location in the memory that is associated with a read command, wherein the unique identifier is associated with one of the plurality of zones and wherein the physical location comprises a physical address;
means for searching for the unique identifier in a hash table that tracks how many times each of the plurality of zones has been read;
means for, in response to finding the unique identifier in the hash table, increasing a counter value in an entry in the hash table that is associated with the unique identifier;
means for determining whether the counter value exceeds a threshold; and
means for, in response to determining that the counter value exceeds the threshold, moving the data associated with the zone to a faster memory for faster reading of the data instead of performing a read scrub operation on an entirety of the block based on a number of times the block has been read.
18. The data storage device of claim 17 , wherein the data is stored in multi-level cell memory and the faster memory comprises single-level cell memory.
19. The data storage device of claim 17 , wherein the unique identifier is generated from one or more of the following: a metablock number and a plane-block number.
20. The data storage device of claim 17 , wherein the unique identifier is generated from one or more of the following a physical block number and a wordline zone number.