Technique for copying unallocated logical regions of thin logical units
A technique for use in managing data storage in a data storage system is disclosed. A first and second data storage commands (DSC) are received from a storage driver stack. Determining if the first DSC and the second DSC are both related aspects of a combined storage command and if so, establishing a pairing structure to pair the first DSC and the second DSC together. Fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure.
1. A method performed by a mapping driver of a computing device operating as a data storage system, the method comprising:
receiving, using a processor, from a storage driver stack, a first data storage command (DSC);
receiving, using a processor, from the storage driver stack, a second DSC;
determining, using a processor, that the first DSC and the second DSC are both related aspects of a combined storage command;
in response to determining, establishing, using a processor, a pairing structure to pair the first DSC and the second DSC together; and
fulfilling, using a processor, the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure, wherein:
the combined storage command is a copy command issued by a remote host instructing the data storage system to copy data from a source location to a destination location;
the first DSC is a source command directing the data storage system to copy from the source location, the source command specifying a source device, a source offset, and a length; and
the second DSC is a destination command directing the data storage system to copy to the destination location, the destination command specifying a destination device and a destination offset.
2. The method of claim 1 wherein the first DSC is received prior to the second DSC and the method further comprises:
successfully completing the combined storage command;
in response to successfully completing, reporting success as response to the first DSC; and
in response to successfully completing, refraining from responding to the second DSC.
3. The method of claim 1 wherein the method further comprises:
receiving a cancellation command directing the data storage system to cancel the combined storage command prior to successfully completing the combined storage command;
in response to receiving the cancellation command, reporting an error as response to the first DSC; and
in response to receiving the cancellation command, reporting an error as response to the second DSC.
4. The method of claim 1 wherein establishing the pairing structure includes:
creating a source descriptor structure that specifies the source device, the source offset, and the length;
creating a destination descriptor structure that specifies the destination device and the destination offset;
inserting a reference to the destination descriptor structure within the source descriptor structure; and
inserting a reference to the source descriptor structure within the destination descriptor structure.
5. The method of claim 4 wherein fulfilling the combined storage command includes sending the source descriptor structure and the destination descriptor structure to an address translation module configured to:
translate the source location from a logical source address to a physical source address; and
translate the destination location from a logical destination address to a physical destination address.
6. The method of claim 1 wherein fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure includes:
translating the source location from a logical source address to a physical source address;
translating the destination location from a logical destination address to a physical destination address; and
sending a copy DSC to a physical storage driver directing the physical storage driver to copy data from the physical source address to the physical destination address, the physical storage driver being able to fulfill the copy DSC without communicating with any driver in the storage driver stack above the mapping driver.
7. The method of claim 1 wherein receiving the second DSC from the storage driver stack includes:
in response to receiving the first DSC, sending a request up the storage driver stack requesting another DSC having a same combined storage command identifier as the first DSC; and
in response to sending the request up the storage driver stack, receiving the second DSC from the storage driver stack, the second DSC having the same combined storage command identifier as the first DSC.
8. A method performed by a mapping driver of a computing device operating as a data storage system, the method comprising:
receiving, using a processor, from a storage driver stack, a first data storage command (DSC);
receiving, using a processor, from the storage driver stack, a second DSC;
determining, using a processor, that the first DSC and the second DSC are both related aspects of a combined storage command;
in response to determining, establishing, using a processor, a pairing structure to pair the first DSC and the second DSC together; and
fulfilling, using a processor, the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure, wherein:
the combined storage command is a mirrored unmap command issued by a remote host instructing the data storage system to unmap data from both a first destination location and a second destination location in a mirrored fashion;
the first DSC is a first unmap command directing the data storage system to unmap the data from the first destination location, the first unmap command specifying a first logical deallocation descriptor structure; and
the second DSC is a second unmap command directing the data storage system to unmap the data from the second destination location, the second write command specifying a second logical deallocation descriptor structure.
9. The method of claim 8 wherein fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure includes:
translating the first destination location from a first logical destination address to a first physical destination address;
translating the second destination location from a second logical destination address to a second physical destination address; and
sending a copy DSC to a physical storage driver directing the physical storage driver to copy data from first physical destination address to the second physical destination address, the physical storage driver being able to fulfill the copy DSC without communicating with any driver in the storage driver stack above the mapping driver.
10. A computer program product comprising a non-transitory computer-readable storage medium storing instructions, which, when executed by a computing device cause the computing device to operate a mapping driver of a data storage system by:
receiving, using a processor, from a storage driver stack, a first data storage command (DSC);
receiving, using a processor, from the storage driver stack, a second DSC;
determining, using a processor, that the first DSC and the second DSC are both related aspects of a combined storage command;
in response to determining, establishing, using a processor, a pairing structure to pair the first DSC and the second DSC together; and
fulfilling, using a processor, the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure, wherein:
the combined storage command is a copy command issued by a remote host instructing the data storage system to copy data from a source location to a destination location;
the first DSC is a source command directing the data storage system to copy from the source location, the source command specifying a source device, a source offset, and a length; and
the second DSC is a destination command directing the data storage system to copy to the destination location, the destination command specifying a destination device and a destination offset.
11. An apparatus comprising:
persistent data storage; and
control circuitry coupled to memory configured to execute a mapping driver of a data storage system by:
receiving, using a processor, from a storage driver stack, a first data storage command (DSC);
receiving, using a processor, from the storage driver stack, a second DSC;
determining, using a processor, that the first DSC and the second DSC are both related aspects of a combined storage command directed at the persistent data storage;
in response to determining, establishing, using a processor, a pairing structure to pair the first DSC and the second DSC together; and
fulfilling, using a processor, the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure, wherein:
the combined storage command is a copy command issued by a remote host instructing the data storage system to copy data from a source location to a destination location;
the first DSC is a source command directing the data storage system to copy from the source location, the source command specifying a source device, a source offset, and a length; and
the second DSC is a destination command directing the data storage system to copy to the destination location, the destination command specifying a destination device and a destination offset.