Method and apparatus for managing data objects of a data storage system
Techniques for managing data objects of a data storage system are described herein. According to one embodiment, a perfect hash function is generated for data objects stored in a data storage system. For each of the data objects, a hash operation is performed using the perfect hash function to indicate whether the respective data object is alive. Resources associated with the respective data object is reclaimed if it is determined that the respective data object is not alive based on a result of the hash operation using the perfect hash function, where the reclaimed resources are released back to the data storage system as free resources. Other methods and apparatuses are also described.
1. A computer-implemented method for managing data objects of a data storage system, the method comprising:
in response to a request to reclaim resources from a plurality of data objects stored in the data storage system, generating a hash function based on an analysis of identifiers of the plurality of data objects, wherein the data storage system stores a plurality of logical data objects, each logical data object being associated with one or more of the data objects;
determining whether each of the plurality of data objects is alive, including
maintaining a live table having a plurality of entries, each entry being associated with one of the plurality of data objects,
for each of the plurality of data objects, performing a hash operation using the hash function to indicate whether the respective data object is alive, wherein a live data object is being referenced by another data object in the data storage system, and
for each data object that is alive, marking a corresponding entry of the live table to indicate that the corresponding data object is alive; and
reclaiming a resource associated with each data object that has not been marked alive, wherein the reclaimed resource is released back to the data storage system as a free resource.
2. The method of claim 1 , wherein the hash function is a perfect hash function.
3. The method of claim 2 , wherein an identifier of a data object is generated based on content of the data object by performing a hash operation on at least a portion of the content of the data object.
4. The method of claim 2 , wherein the perfect hash function is configured to map each of the identifiers of a data object to a unique hash value without collision, and wherein the unique hash value is used to indicate whether a particular data object is alive.
5. The method of claim 2 , wherein the perfect hash function is a minimal perfect hash function that maps a set of N elements to a range of N values, and wherein an identifier of a data object is used as an input to the minimal perfect hash function.
6. The method of claim 1 , wherein a resource associated with the respective data object is reclaimed if the entry of the live table associated with the respective data object has not been marked, and wherein the resource is reclaimed after all live data objects have been marked in the live table using the hash function.
7. The method of claim 1 , wherein the live table comprises a bit vector having a plurality of bits, wherein each of the plurality of data objects is associated with a bit in the bit vector, and wherein the bit vector is indexed based on a hash value obtained from the hash function.
8. The method of claim 1 , wherein the storage space associated with the respective data object is overwritten with at least one predetermined bit pattern if it is determined that the respective data object is not alive based on a result of the hash operation using the hash function.
9. A non-transitory machine-readable medium having instructions which when executed by a machine, cause the machine to perform a method for managing resources of a data storage system, the method comprising:
in response to a request to reclaim resources from a plurality of data objects stored in the data storage system, generating a hash function based on an analysis of identifiers of the plurality of data objects, wherein the data storage system stores a plurality of logical data objects, each logical data object being associated with one or more of the data objects;
determining whether each of the plurality of data objects is alive, including
maintaining a live table having a plurality of entries, each entry being associated with one of the plurality of data objects,
for each of the plurality of data objects, performing a hash operation using the hash function to indicate whether the respective data object is alive, wherein a live data object is being referenced by another data object in the data storage system, and
for each data object that is alive, marking a corresponding entry of the live table to indicate that the corresponding data object is alive; and
reclaiming a resource associated with each data object that has not been marked alive, wherein the reclaimed resource is released back to the data storage system as a free resource.
10. The non-transitory machine-readable medium of claim 9 , wherein the hash function is a perfect hash function.
11. The non-transitory machine-readable medium of claim 10 , wherein an identifier of a data object is generated based on content of the data object by performing a hash operation on at least a portion of the content of the data object.
12. The non-transitory machine-readable medium of claim 10 , wherein the perfect hash function is configured to map each of the identifiers of a data object to a unique hash value without collision, and wherein the unique hash value is used to indicate whether a particular data object is alive.
13. The non-transitory machine-readable medium of claim 10 , wherein the perfect hash function is a minimal perfect hash function that maps a set of N elements to a range of N values, and wherein an identifier of a data object is used as an input to the minimal perfect hash function.
14. The non-transitory machine-readable medium of claim 9 , wherein a resource associated with the respective data object is reclaimed if the entry of the live table associated with the respective data object has not been marked, and wherein the resource is reclaimed after all live data objects have been marked in the live table using the hash function.
15. The non-transitory machine-readable medium of claim 9 , wherein the live table comprises a bit vector having a plurality of bits, wherein each of the plurality of data objects is associated with a bit in the bit vector, and wherein the bit vector is indexed based on a hash value obtained from the hash function.
16. The non-transitory machine-readable medium of claim 9 , wherein the live table comprises a bit vector having a plurality of bits, wherein each of the plurality of data objects is associated with a bit in the bit vector, and wherein the bit vector is indexed based on a hash value obtained from the hash function.
17. The non-transitory machine-readable medium of claim 9 , wherein the storage space associated with the respective data object is overwritten with at least one predetermined bit pattern if it is determined that the respective data object is not alive based on a result of the hash operation using the hash function.
18. A data storage system, comprising:
a processor; and
a memory coupled to the processor to store instructions, which when executed by the processor, cause the processor to
in response to a request to reclaim resources from a plurality of data objects stored in the data storage system, generate a hash function based on an analysis of identifiers of the plurality of data objects, wherein the data storage system stores a plurality of logical data objects, each logical data object being associated with one or more of the data objects,
determine whether each of the plurality of data objects is alive, including
maintaining a live table having a plurality of entries, each entry being associated with one of the plurality of data objects,
for each of the plurality of data objects, performing a hash operation using the hash function to indicate whether the respective data object is alive, wherein a live data object is being referenced by another data object in the data storage system, and
for each data object that is alive, mark a corresponding entry of the live table to indicate that the corresponding data object is alive, and
reclaim a resource associated with each data object that has not been marked alive, wherein the reclaimed resource is released back to the data storage system as a free resource.
19. The system of claim 18 , wherein the hash function is a perfect hash function.
20. The system of claim 19 , wherein an identifier of a data object is generated based on content of the data object by performing a hash operation on at least a portion of the content of the data object.
21. The system of claim 19 , wherein the perfect hash function is configured to map each of the identifiers of a data object to a unique hash value without collision, and wherein the unique hash value is used to indicate whether a particular data object is alive.
22. The system of claim 19 , wherein the perfect hash function is a minimal perfect hash function that maps a set of N elements to a range of N values, and wherein an identifier of a data object is used as an input to the minimal perfect hash function.
23. The system of claim 18 , wherein the live table comprises a bit vector having a plurality of bits, wherein each of the plurality of data objects is associated with a bit in the bit vector, and wherein the bit vector is indexed based on a hash value obtained from the hash function.
24. The system of claim 18 , wherein the storage space associated with the respective data object is overwritten with at least one predetermined bit pattern if it is determined that the respective data object is not alive based on a result of the hash operation using the hash function.