Facilitating access to fragmented snapshot data

Patent metadata

Field	Value
Publication number	US-12339805-B2
Application number	US-202318362088-A
Country	US
Kind code	B2
Filing date	Jul 31, 2023
Priority date	Jul 31, 2023
Publication date	Jun 24, 2025
Grant date	Jun 24, 2025

Abstract

Techniques are provided to facilitate access to fragmented snapshot data. For example, a storage control system generates a snapshot data structure of a storage volume. The snapshot data structure comprises plurality of nodes comprising a volume node and one or more snapshot nodes, the volume node is configured to store new and updated data that is written to logical offsets of the storage volume, and the one or more snapshot nodes comprise point-in-time copies of data of the storage volume taken at different times. The storage control system adds an entry for the volume node in a metadata structure associated with the snapshot data structure, wherein the entry comprises a reference to a physical location of data held by a given one of the snapshot nodes at a given logical offset of the storage volume.

First claim

What is claimed is:

1. A method, comprising:
generating, by a storage control system, a snapshot data structure of a storage volume, wherein the snapshot data structure comprises plurality of nodes comprising a volume node and one or more snapshot nodes, wherein the volume node is configured to store data that is written to one or more logical offsets of the storage volume, and wherein the one or more snapshot nodes comprise point-in-time copies of data of the storage volume taken at different times;
for a given logical offset of the storage volume for which data has not been stored by the volume node, the storage control system adding a volume node entry for the given logical offset in a metadata structure associated with the snapshot data structure, wherein the volume node entry comprises a reference which points to a physical location of a current version of a data block held by a given one of the snapshot nodes other than the volume node at the given logical offset of the storage volume, wherein the reference is determined by the storage control system using existing referencing metadata associated with the storage volume; and
utilizing, by the storage control system, the reference in the volume node entry of the volume node in the metadata structure to access the current version of the data block held by the given one of the snapshot nodes.

2. The method of claim 1 , wherein the snapshot data structure comprises a snapshot tree structure in which the one or more snapshot nodes comprise a chain of incremental snapshots taken of the storage volume at different times.

3. The method of claim 1 , wherein:
the metadata structure associated with the snapshot data structure comprises a mapping table data structure comprising a metadata entry for each logical offset in each logical address space of each node of the snapshot data structure which holds a data block of the storage volume; and
each metadata entry comprises a key-value pair, wherein the key comprises a combination of a node identifier and logical offset and the value comprises a physical location of a data block stored at the logical offset in the logical address space of the node.

4. The method of claim 1 , wherein the existing referencing metadata comprises deduplication reference metadata which is utilized by the storage control system to determine the reference to the physical location of data held by the given one of the snapshot nodes at the given logical offset of the storage volume.

5. The method of claim 1 , further comprising, for a given sequence of logical offsets of the storage volume for which data has not been stored by the volume node, the storage control system adding a sequence of volume node entries for the given sequence of logical offsets in the metadata structure associated with the snapshot data structure, wherein each volume node entry of the sequence of volume node entries comprises a respective reference which points to a physical location of a current version of a data block held by a given one of the snapshot nodes other than the volume node at a respective logical offset of the given sequence of logical offsets of the storage volume, wherein each reference is determined by the storage control system using the existing referencing metadata associated with the storage volume.

6. The method of claim 5 , further comprising performing, by the storage control system, a sequential read operation to sequentially access the data blocks in the sequence of logical offsets of the storage volume, which are held by the one or more snapshot nodes, by accessing the sequence of volume node entries for the volume node in the metadata structure to determine the physical location of the data blocks.

7. The method of claim 5 , further comprising:
determining, by the storage control system, a current input/output (I/O) workload associated with the storage volume;
adding the sequence of entries for the volume node in the metadata structure, in response to determining the current I/O workload comprises a read I/O workload; and
refraining from adding the sequence of volume node entries for the volume node in the metadata structure, in response to determining the current I/O workload comprises a write intensive I/O workload.

8. The method of claim 5 , further comprising:
determining, by the storage control system, a fragmentation level of the snapshot data structure; and
adding the sequence of volume node entries for the volume node in the metadata structure, in response to determining that the fragmentation level of the snapshot data structure exceeds a threshold.

9. A computer program product comprising a non-transitory processor-readable storage medium having stored therein program code of one or more software programs, wherein the program code when executed by at least one processing device causes the at least one processing device to implement a storage control system that is configured to perform a snapshot management process which comprises:
generating a snapshot data structure of a storage volume, wherein the snapshot data structure comprises plurality of nodes comprising a volume node and one or more snapshot nodes, wherein the volume node is configured to store data that is written to one or more logical offsets of the storage volume, and wherein the one or more snapshot nodes comprise point-in-time copies of data of the storage volume taken at different times;
for a given logical offset of the storage volume for which data has not been stored by the volume node, adding a volume node entry for the given logical offset in a metadata structure associated with the snapshot data structure, wherein the volume node entry comprises a reference which points to a physical location of a current version of a data block held by a given one of the snapshot nodes other than the volume node at the given logical offset of the storage volume, wherein the reference is determined by the storage control system using existing referencing metadata associated with the storage volume; and
utilizing the reference in the volume node entry of the volume node in the metadata structure to access the current version of the data block held by the given one of the snapshot nodes.

10. The computer program product of claim 9 , wherein the snapshot data structure comprises a snapshot tree structure in which the one or more snapshot nodes comprise a chain of incremental snapshots taken of the storage volume at different times.

11. The computer program product of claim 9 , wherein:
the metadata structure associated with the snapshot data structure comprises a mapping table data structure comprising a metadata entry for each logical offset in each logical address space of each node of the snapshot data structure which holds a data block of the storage volume; and
each metadata entry comprises a key-value pair, wherein the key comprises a combination of a node identifier and logical offset and the value comprises a physical location of a data block stored at the logical offset in the logical address space of the node.

12. The computer program product of claim 9 , wherein the existing referencing metadata comprises deduplication reference metadata which is utilized to determine the reference to the physical location of data held by the given one of the snapshot nodes at the given logical offset of the storage volume.

13. The computer program product of claim 9 , for a given sequence of logical offsets of the storage volume for which data has not been stored by the volume node, further comprising program code for adding a sequence of volume node entries for the given sequence of logical offsets in the metadata structure as

Assignees

• Dell Products Lp

Inventors

• Shatsky Yosef
• Tal Doron

Classifications

• G06F16/128 Primary

  Details of file system snapshots on the file-level, e.g. snapshot creation, administration, deletion (error detection or correction of the data by redundancy in operations or in hardware G06F11/14, G06F11/16) · CPC title

• G06F16/164

  File meta data generation · CPC title

• G06F11/3409

  for performance assessment · CPC title

• G06F2201/84

  Using snapshots, i.e. a logical point-in-time copy of the data · CPC title

• G06F16/122 Primary

  using management policies (point-in-time backing up or restoration of persistent data G06F11/1446; file migration policies for HSM systems G06F16/185) · CPC title